关键词: 四川盆地, 须家河群, 安县运动, 印支运动, 龙门山

Abstract:

The Late Triassic Xujiahe Group in West Sichuan Basin consists of two kinds of ab-solutely different depressed sediments.The lower basin is the depression of continental margin while the upper basin is fore deep depression resulted by intensive orogenic move-ment.The important tectonic movement leading to the above mentioned transform inquality now have been proved and is named Anxian orogenic movement(Anxian Move-ment for short),which corresponds to the second episode of the Indo-China movement—Pre-Rhaetic orogenic episode.The 4th and 5th members of the Xujiahe Group are absencein the Longmen Mountains and its foreland area,and the Jurassic Systen overlapped onunconformity,thus leading to the misunderstanding for the movement time,that is,themovement was considered to occur in between the end of the Triassic and the fore of Jurassic for a long time.The Anxian movement is not a locally geological phenomena,buta signficant geological event of Chinese Plate colliding with exotic plate.The foreland of the Longmen Mountains is the front edge of intensive zone of the orogenic movement,and the boundary between back-arc overthrust and regressive arc basin that is the boundary between active and stable belts.This movement plays an important role in hydrocarbon dis-tribution to the west part of Sichuan Basin as well as the whole region.