上扬子克拉通北部晚古生代-中三叠世的沉积盆地是在勉-略洋盆南侧发展起来的被动大陆边缘盆地,在泥盆纪-中二叠世以稳定沉降为主,向北以碳酸盐岩缓坡与台地向勉略洋盆过渡;中二叠世末期受峨眉地裂运动影响形成隆坳相间的格局;早一中三叠世构造体制由伸展变为挤压,沉积建造由开阔海碳酸盐岩台地逐渐向半局限台地、半封闭海湾膏盐湖相以及陆相碎屑岩含煤岩系过渡。该陆缘盆地经历了晚三叠世上扬子北缘前陆盆地、中侏罗世一早白垩世川西、川北前陆盆地,以及晚白垩世至今构造残留盆地的改造。其中,晚三叠世须三一须六期上扬子北缘前陆盆地的前缘隆起大致沿汶川、剑阁和万源一线分布。热年代学分析结果表明,汶川、剑阁和万源一线以南的上二叠统烃源岩在早中生代始终处于埋藏增温状态,只是自晚白垩世才进入抬升降温阶段,呈“同代”烃源岩的特征;而汶川、剑阁和万源一线以北的龙门山、米仓山和大巴山山前冲断地区,上二叠统烃源岩则围绕生烃窗经历了多次增温和降温过程,热演化历史复杂,呈“隔代”烃源岩的特征。因此,对于上扬子克拉通北部晚古生代一中三叠世陆缘盆地的勘探,汶川、剑阁和万源一线以南比其北侧更有利。
Late Paleozoic-Middle Triassic sedimentary basin in the north part of Upper Yangtze Carton is a passive continental margin basin that developed in the south side of Mian-Lue ocean. This basin transited from carbonate ramp and platform to Mian-Lue ocean at the background of stable subsidence from Devonian to Middle Permian, and was characterized by the formation of structural framework with alternative depressions and upheavals affected by Emei Tafrogeny at the end of Middle Permian. In Early-Middle Triassic, sedimentary formation transited gradually from open carbonate platform environment to semi-restricted platform phase, semi-enclosed bay gypsum salt lake facies, terrestrial clastic rock with coal bearing formation for tectonic regime transferring from extensional to compressional. This continental marginal basin was intensively modified in the foreland stage of the northern Upper Yangtze in Late Triassic, northern Sichuan and western Sichuan in Middle-Late Jurassic, and in the residual structure basin stage from Late Cretaceous to present. The analysis of thermal chronology showed that, to the south of Late Triassic Jiange paleo-uplift, the rapid uplift of orogenic belt around basin in Middle-Late Jurassic caused quick filling and warming in cover area of basin at the background of low heat flow, which caused the source rocks of Upper Permian and Upper Triassic to enter oil window rapidly. But to the north of Late Triassic Jiange paleo-uplift, the source rock of Upper Permian in the piedmont thrust belts of Longmen, Micang and Daba Mountains had entered oil window at Early-Middle Triassic, and was uplifted to the top of oil window again by Indo-China movement in Later Triassic, which implies the complicated W- shaped thermal evolution path, and "alternate-generation" attribute of source rock. So, the buried area of basin, to south of Wenchuan, Jiange, and Wanyuan, is more favorable than the piedmont thrust belt of northern Longmen, Micang and Daba Mountains from the view of strategic area selection.