四川盆地西部陆相碎屑岩层系演化与构造变形特征

摘要

Thick continental clastic rocks,which are important exploration layers,are deposited in the western Sichuan Basin.Based on the analysis of stratigraphic distribution,cross sections and regional setting,the evolution processes and structural deformation of continental clastic rocks in the western Sichuan Basin were discussed.The results show that because of the differential uplifting of peripheral orogens,the depocenters of continental clastic rocks in Sichuan Basin migrate regularly;the depocenter locates in the western Sichuan foreland basin in Late Triassic, and then shifts into the northeastern Sichuan foreland basin in Early-Middle Jurassic; the continental clastic rocks in the western Sichuan Basin are influenced by multi-phase tectonic events,including the Indosinan,Yanshanian and Himalayan movements;during the various tectonic movements,the basin types of the western Sichuan Basin change from an intra-cratonic rift basin in Early-Middle Triassic to a continental margin basin in Early Late Triassic,and then to an intracontinental foreland basin in the subsequent stages;thrust faults and folds are the most distinctive deformation characteristics of the continental clastic rocks in the western Sichuan Basin,and some major faults also have weak strike-slipping movement;the main structural styles involve imbricate thrust systems,pop-ups,fault-related folds and klippes,etc.;the zonation of structural deformation is horizontal,which has also controlled the zonation of traps.%四川盆地西部地区沉积了较厚的陆相碎屑岩，同时也是重要的勘探目的层系。根据地层平面展布特征以及剖面解释结果，并结合区域地质背景，分析了四川盆地西部陆相碎屑岩层系的演变过程及其构造变形特征。结果表明：受周缘造山带在不同时期差异隆升的影响，四川盆地陆相碎屑岩层系的沉积中心发生了有规律的迁移，从晚三叠世时的川西前陆盆地迁移至早—中侏罗世时的川东北前陆盆地；四川盆地西部地区陆相碎屑岩层系遭受了印支期、燕山期和喜山期等多期构造事件的影响，盆地属性也随之发生改变，从陆相碎屑岩层系沉积前的克拉通内裂陷盆地转变为晚三叠世早期的大陆边缘盆地，并最终演变为现今的陆内前陆盆地；四川盆地西部陆相碎屑岩层系构造变形以逆冲推覆和褶皱变形为主，兼具弱走滑作用，主要发育叠瓦冲断带、背冲断块、断层相关褶皱、飞来峰等构造样式，同时表现出一定的横向分带性，并控制了圈闭发育的分带性。