大型陆相坳陷型沉积盆地原型恢复方法——以新生代柴达木盆地为例

A method of prototype restoration of large depressions with terrestrial sediments: A case study from the Cenozoic Qaidam Basin

陆相坳陷型沉积盆地通常发育在克拉通的内部差异沉降和裂谷盆地后期的热沉降等不同的大地构造阶段,是一类独特而又十分重要的沉积盆地。本文基于该类盆地的特点,提出了综合利用盆地沉积相、残余厚度图、区域构造大剖面及其平衡恢复等多方面资料对其盆地原型进行恢复的方法和流程,具体包括以残余沉积相恢复盆地原始边界、以平衡剖面恢复盆地原始形态、以关键钻井资料与平衡剖面相结合恢复原始沉积厚度。该方法消除了构造运动对盆地形态的改变,真正将盆地原型纳入到其原始形态框架下进行研究。本文还利用该方法对柴达木盆地新生代各地层沉积时的盆地原型分别进行了恢复,并据此对其新生代的沉积演化进行了分析,结果表明柴达木盆地新生代的沉积格局变化与阿尔金断裂的活动息息相关。

Depressions with terrestrial sediments is a unique and very important kind of sedimentary basins on earth,which usually develops by differential subsidence within Craton and / or thermal subsidence in the late stage of rift basin. In this paper,based on the characteristics of this type of basin,we put forward a method and workflow on basin Prototype reconstruction using a comprehensive analysis of sedimentary facies,isomaps of remnant thickness,regional cross-sections and related balance sections. The method and workflow include restoring the original boundaries of the basin using residual sedimentary facies,the original shapes during different stages using balanced cross-sections,and the original sediment thickness using relevant exploratory well data and balanced crosssections. By this method we can research the basin prototype within the original shape of basin,which eliminates the effect of later tectonic alteration. We analyzed the Cenozoic Prototype of the Qaidam Basin in northern Tibetan Plateau based on the above workflow.The result shows that the change of sedimentary patterns of the Qaidam Basin over time was closed related to the activities of the Altyn Tagh Fault.