大巴山前陆盆地晚三叠世—侏罗纪沉积中心的迁移及古流向

晚三叠世上扬子北缘沉积中心主要在川西地区,但在大巴山前缘的达县—万源之间开始出现一个次级沉积中心,反映晚三叠世大巴山前陆盆地初始沉降;早-中侏罗世早期,上扬子北缘沉积中心东移到大巴山前缘,具有两个沉积中心,但沉积厚度不大;中侏罗世中、晚期,两个沉积中心向大巴山一侧北移,沉积厚度巨大,反映该期为大巴山前陆盆地强烈沉降期;晚侏罗世,两个沉积中心分别向东、西两侧迁移,东、西分异明显,沉积厚度较大,反映晚侏罗世大巴山前陆盆地的持续稳定沉降。

Migration of the Late Triassic-Jurassic depocenter and paleocurrent direction in the Dabashan foreland basin

In the Late Triassic,the western Sichuan Basin was the primary depocenter in the northern part of the upper Yangtze area.Meanwhile,a secondary depocenter took shape in the area between Daxian and Wanyuan in front of Dabashan Mountain,indicating the initial subsidence of the Dabashan foreland basin in the Late Triassic.During the Early Jurassic to the early of Middle Jurassic,the depocenter in the northern part of the upper Yangtze area moved eastward to the front of the Dabashan Mountain.At that time,there were two co-existing depocenters with their depositional thickness not too big.In the middle and late of Middle Jurassic,the two depocenters shifted northward to Dabashan Mountain with great thickness of sedimentary formation,indicating dramatic subsidence of the foreland basin.In the Late Jurassic,the two depocenters migrated eastward and westward respectively with considerable difference in sedimentation and relatively bigger thickness,revealing the continuous and stable subsidence of the foreland basin.