中国西部新生代陆内前陆盆地迁移过程及其构造指示意义

Migration Processes of the Cenozoic Intracontinental Foreland Basins in Western China and Their Tectonics Implications

中国西部新生代陆内前陆盆地的迁移过程反映了与其耦合的造山带的缩短隆升历史。通过综述恢复前陆盆地迁移过程的研究方法及其与地壳缩短过程的定量关系,阐明了前陆盆地迁移过程的构造指示意义。横跨前陆盆地的地震反射剖面可显示盆地内的地层上超或砾岩—砂岩过渡带迁移,反映盆地迁移过程;结合磁性地层学约束的地层年龄,可获得迁移速率;该速率的变化对应前陆盆地基底相对造山带的俯冲速率变化,反映造山带吸收的地壳水平缩短速率变化。通过对比分析西昆仑山北侧及天山南、北侧的陆内再生前陆盆地的迁移过程,发现约30 Ma以来西昆仑山和天山的地壳缩短速率变化趋势和变形模式均不相同,可能反映二者造山的动力学机制差异。该方法未来还有望应用于青藏高原东北缘以恢复高原生长过程。

The migration processes of the Cenozoic intracontinental foreland basins in western China provide valuable insights into the shortening and uplifting histories of coupled orogenic belts.A comprehensive review of the research methodologies used to reconstruct foreland basin migration and its quantitative relationship with crustal shortening enables us to uncover the structural implications of this process.Seismic reflection profiles crossing the foreland basins image the stratal onlaps and conglomerate-sandstone transitions in the basins.Based on the interpretations of seismic profiles,the migration rate of foreland basins can be determined by integrating stratigraphic age constraints derived from magnetostratigraphy.The variations in the rates correspond to the variations in the underthrusting rates of the foreland basin basement relative to the orogenic belts,revealing changes in the horizontal crustal shortening rates absorbed by the orogenic belts.Through a comparative analysis of the migration processes of the rejuvenated intracontinental foreland basins on the northern side of the West Kunlun Mountains and the southern and northern sides of the Tianshan Mountains,these two mountains contrast markedly in terms of crustal shortening rates and deformation patterns since approximately 30 Ma.The contrast between these mountains indicates differences in their dynamic mechanisms.Furthermore,this method holds great potential for future applications in unraveling the growth process of the northeastern margin of the Qinghai-Tibet Plateau.