【摘要】 强烈不对称的楔型地层是前陆盆地的典型特点,前隆带地层大量减薄或缺失、前隆带与前渊带三级层序的细分对比 是建立前陆盆地层序地层格架的关键.结合前人对前陆盆地岩石圈挠曲变形模拟的认识,经过对库车前陆盆地的实例分析 表明,前陆盆地挤压构造活动引起前渊带沉降、而前隆带隆升,导致可容纳空间发育在横向上不协调.可容纳空间的不协调 发育与前隆的产生和迁移的动态演化过程相伴随:在构造的活动期,前隆隆升并向冲断带迁移,盆地变窄变深,可容纳空间 发育的不协调性逐渐增强;在构造宁静期,盆地变宽变浅,可容纳空间整体性发育.因此,前陆盆地二级层序在地震剖面上 具双层结构(如库车盆地侏罗系、白垩系卡普沙良群),其下层为一组楔状、向冲断带收缩的退积反射;上层反射呈带状、延 续范围广.层序的对比模式为:在二级层序的底部,三级层序向克拉通渐次超覆;在二级层序的中部,三级层序的分布向冲 断带渐次收缩;在二级层序的上部,三级层序分布广泛,可对比性强(如库车盆地下第三系).更多还原

【Abstract】 From the forebulge to the foredeep of a foreland basin, the stratigraphic framework appears asymmetrical and wedge-shaped. The stratigraphic sequence at the forebulge is thin or absent. Research on the Kuqa foreland basin in Northern Tarim basin and previous studies on lithospheric flexural simulations of foreland basins show that accommodation space from the forebulge to the foredeep develops inconsistently due to compressional tectonism, which results in the forebulge rising while the foredeep subsides. This inconsistency is dynamically associated with the formation and migration of the forebulge. In an active tectonic phase the forebulge rises and migrates gradually toward the thrust-fault belt, which results in the basin narrowing and deepening, and the development of accommodation space becoming more and more inconsistent. In an inactive tectonic phase the basin is wide and shallow and accommodation space develops consistently. Therefore, the reflection configuration of a second-order sequence is two-layered in seismic sections such as the Jurassic and the Kapushaliang Group, Cretaceous of the Kuqa basin: the lower layer is a group of wedge-shaped, regressive reflections shrinking gradually toward the thrust-fault belt; the upper layer is a group of strap-shaped, widespread reflections. Further, the correlation model showed that the third-order sequences in the lower part of a second-order sequence onlapped gradually toward the craton, which indicates the initial tectonism and the formation of the forebulge; that the third-order sequences in the middle part gradually decrease in size toward the thrust-fault belt, corresponding to intense tectonism; that the third-order sequences in the upper part are widely distributed, corresponding to an inactive tectonic phase such as the Lower Tertiary of the Kuqa basin.更多还原