北京平原第四系的三维结构

北京平原地处山区与华北平原的结合部位,是山前第四纪冲洪积扇发育区.由于山前冲洪积扇内部结构复杂,相变迅速.海相、湖相的工作方法不能满足要求.本文通过对北京平原第四纪沉积特征的分析,提出北京平原由第四纪冲洪积扇群和沉积凹陷几个地质单元组合而成.在此基础上总结了近几年在山前冲洪积扇区的工作经验,提出了以冲洪积扇和沉积凹陷为地质单元,以建立基准孔网,结合钻孔和物探资料,并通过绘制剖面组进而构建第四系三维结构的方法.利用该方法建立了北京平原第四系的三维结构模型.了解北京平原第四系的三维结构对研究水文地质、工程地质和环境地质都有重要意义,可以为城市规划、城市建设提供重要的资料.

3D Quaternary geological structure of Beijing plain

Beijing plain,located at the junction of the Yanshan Mountains and the North China Plain,consists of sea facies,lacustrine facies,and alluvial sediments.Due to its complicated characteristics,traditional geological survey methods are not applicable in this area.In order to get high-precision information of geological structure in Beijing plain,this paper presents a new practical survey method,whose principles are as follows:first,the entire alluvial-proluvial fan is subdivided into several subsections based on geological structures and sedimentary features;after that,new high-resolution geological cross sections are created by using framework borehole data,geophysical data and historical research results;and then,the characteristics of Quaternary sediments in each geological element is well described;finally,the 3D geological model of Quaternary is built by using computer techniques and the GIS system of Beijing plain.This model can play an important role in city planning and construction and also promote the development of hydrogeology,engineering geology and environmental geology in Beijing.