摘要
渭河裂谷盆地是汾渭裂谷系构造的重要组成部分,是喜山期以来秦岭造山带北缘在环太平洋构造域与特提斯构造域联合作用的产物。它的演化经历了前燕山期挤压收缩所造成的正扇形断褶隆起;早喜山期初始扩张断陷;中喜山期的强烈伸展裂陷和晚喜山期的联合扭动改造作用,而形成现渭河裂谷盆地。
The Weihe rift basin is a Cenozoic rift basin that is located between the Beishan mountains and the Qinling ones. It is also an important component of the Fen-Wei rift system.
The Qinling mountains lie in the southern part of the rift basin, which lies at an over average 2,500 metres above sea level.The Beishan mountains are about 1,000-1,500m above sea level.The rift basin has an average height of 460m above sea level.According to the data from the well W.No.10, drilling in the depth of 5,600m did'nt get through Eogene.The height difference from the Taibaishan to the basement of the Weihe rift basin is about 1,000 metres, which shows that the subsidence range of the rift is very great.
The marginal structures in the northern and southern parts of the Weihe rift basin were characterized by the large-scale fault structural zones that were composed of the structural features with twofold mechanical properties. In them the northern marginal compressive structural zones were made up of the nappe fault subzone, the fault-fold subzone and the fold subzone from the south to the north. The most internal structure zone was a tensile sturct-ural one with the tension-twist properties. This zone consists of the large scale normal fault structures and controls the northern boundary of the Weihe rift basin.The southern marginnl structural zones were the late tension-twist fault zones formed by reforming the early compressive fault zones, which
formed a great geomorphic landscape with the fault scarps, the fault triangular facet and the fault hanging valley.These zones also control the southern boundary of the Weihe rift basin.
The forming of the Weihe rift basin has undergone the following proce-dures: (1) A-type subduction of the Qinling orogenic belt from the Pre-Yanshan stage to the Yanshan stage and the formatinn of the large-scale normal fan upwarping faulted structures in front of the obducting wall; (2) the weathering denudation in the Yanshan stage; ( 3 ) the gradual extended rift in the Himalayan stage; and (4 ) the conjunct twist reformation in the neoid stage.
关键词
裂谷
盆地
构造
断陷
断块
rift basin, compressive fault,tension-twist fault,conjunct twist
