空间数据库技术实现定量古地理研究——以鄂尔多斯盆地中奥陶统一个三级层序的形成时间为例

以沉积层序为时间单位进行岩相古地理研究需要对野外剖面、测井、录井、地震、岩心等海量数据进行定量分析对比,而传统的人工方法往往难以有效地管理并利用这些资料。文中使用空间数据库技术将基础地质数据以自然层为单位,按统一标准定量化处理;并以层序为单位计算、统计、分析,提取厚度、白云岩含量、灰泥含量、陆源碎屑含量等反映沉积环境特征的多种单因素,定量绘制各单因素等值线图。在区域地质背景分析的基础上,将各单因素等值线图叠加分析,并探索定量古地理研究方法——通过单因素复合公式计算值划分古地理单元的边界,最终绘制出古地理图。以鄂尔多斯奥陶系马五组上部一个层序时段(464～466Ma)为例,运用上述方法自动识别出古陆、山丘高地、潮上带、潮间带、潮下带等古地理单元。研究表明,空间数据库技术是实现定量古地理的有效手段。

Application of spatial database in quantitative study of litho-palaeogeography-A case study of a Middle Ordovician sequence interval in Ordos Basin

In the study of sequence litho-palaeogeography,the quantitative analysis,precise calculation and detailed comparison of tremendous geological data,such as field profiles,logging records and seismic curves from different areas,are the basic requirements.In order to obtain a more reliable and precise result,we have developed a method,by using the spatial database to manage effectively the data that cannot be treated by traditional ways.Various attributes of the basic stratigraphic units and their characteristics,such as sequence thickness,pene-contemporaneous dolostone content,shallow water plaster content,and terrigenous material content,can be fully utilized statistically in facies analysis and in mapping.Based on this analysis,we have exerted single-factor isopachous mapping quantitatively for each of the Ordovician sequences in the basin,and we used a single factor formula to delineate the borders of facies units.Finally synthesis multiple factors have to be used to reconstruct the litho-palaeogeography for each of the sequence intervals.The study shows that the proposed method is quite effective and has a much higher resolution in recognizing litho-paleogeographic subunits than traditional ways.For example,in one of the Middle Ordovician sequence interval(444-446 Ma) of the Ordos Basin,we have successfully mapped the precise distribution of various facies units,such as old land,submarine uplift,up tidal flat,middle tidal flat and down tidal flat.