柴西地区尕斯断陷同生逆断裂构造特征与形成演化

Structural features and evolution of contemporaneous reversed faults in Gas faulted depression in western Qaidam basin

柴达木盆地西部尕斯断陷逆断裂和褶皱构造发育 ,褶皱与断裂紧密伴生 ,断裂位于背斜构造的一侧或两侧 ,各构造层高点上下铅直叠合。大多数断裂对沉积具有明显控制作用 ,尕斯断陷北西西向区域性同生逆断裂控制着局部沉积凹陷(生油凹陷 )的分布和范围 ,沉积中心位于断裂下降盘附近 ;而规模较小的同生逆断裂主要发育在凹陷或凸起内部 ,控制着局部构造圈闭的形成和发展。断裂与背斜构造发育不同期 ,断裂形成早 ,为边沉积边逆冲的基底同沉积断裂。背斜构造形成时间较晚 ,为第三纪晚期挤压或压扭性构造应力作用所致。背斜构造在中新世早期以后才显示出顶薄翼厚。

Reversed faults and folds are well developed in Gas faulted depression. The faults, closely accompanying the folds, are located on one side or both sides of anticlines and the highs of each structural layer superimpose vertically. Most faults have obvious control over sedimentation. The regional NWW contemporaneous reversed faults in Gas faulted depression would have controlled the distribution and scope of local sedimentary sags (oil generating sags), the depocenters of which are located near the downthrow blocks; while the relatively small contemporaneous reversed faults are mainly developed within sags or swells and would have controlled the formation and development of local structural traps. The faults and anticlines were not developed at the same time. The faults were formed earlier on the basement as synsedimentary faults, which thrusted while depositing. The anticlines were formed later as a result of compressional or compresso torsional structural stress in Late Tertiary. Anticlinal structures did not show synsedimentary characteristics of thin and coarse on the crest, and thick and fine on the limb until the early Miocene.