西秦岭关家沟组地层时代、物源及其构造响应

ON THE AGE,PROVENANCE AND STRUCTURAL RESPONSE OF THE GUANJIAGOU FORMATION IN THE WESTERN QINLING MOUNTAINS

在西秦岭关家沟组贾昌沟砂板岩所夹的硅质岩层中发现晚石炭世和晚二叠世的古生物化石;在关家沟组砾岩中所采的花岗质和火山质砾石,利用氩-氩（40Ar/39Ar）法测年所获得的年龄为晚三叠世。对关家沟组物源及其古水流分析,其古水流方向230°-356°,其物源主要来自南东侧活动大陆边缘的碧口岛弧,且秦岭全面碰撞造山期为早中生代。由此,初步推测关家沟组形成时代可能与秦岭全面碰撞造山为同期——早中生代。

The fossils from siliceous stone in sandy slate from Jiachang channel indicate that the age of the Guanjiagou Formation is Late Carboniferous or Late Permian, while results of 40Ar/39Ar thermochronology of the granitic and volcanic gravels from the Guanjiagou Formation suggest that the age of the Guanjiagou Formation is Late Triassic. The direction of paleocurrent was found to be 230° - 356°and the sediments were found to originate from the southeast Bikou island arc, which is close to the active continental edge based on the provenance and the direction of the paleocurrent. Moreover, it was determined that Guanjiagou Formation may result from the large-scale collision episode in Qinling （ early Mesozoic）. Therefore, it can be primarily presumed that the era for Guanjiagou Formation is early Mesozoic.