Cenozoic structural deformation in the Yuqia-Jiulongshan region, northern Qaidam Basin, China

Based on field geological survey, interpretation of seismic reflection profile and thermochronology dating, this paper systematically studied the structural deformation of the Yuqia-Jiulongshan region in northern Qaidam Basin during the Cenozoic. The results show that the area is primarily dominated by a large box-shaped anticline, with steep limbs and a wide and gently-deformed core. The Mahaigaxiu and Jiulongshan anticlines are secondary folds controlled by secondary faults in the limbs of the box-shaped anticline. Whereas the Yuqia and the Northern Yuqia anticlines are secondary folds within the wide core of the box-shaped anticline. The geometry of the box-shaped anticline is mainly controlled by some high-angle reverse faults with certain right-lateral strike-slip components, displaying distinct positive flower structures in section view. Combining the sedimentary correlation and detrital apatite fission track analysis, we believe that the Yuqia-Jiulongshan region was a paleo-uplift that developed slightly in the early Cenozoic, resulting in the relatively thin Cenozoic strata. The intense deformation that shaped the present-day structural framework occurred in or after the sedimentary period of Shizigou Formation. The Yuqia – Jiulongshan paleo-uplift is adjacent to the Sainan depression that is rich in Lower-Middle Jurassic source rocks, and thus has high potential for future hydrocarbon exploration.

柴达木盆地北缘鱼卡—九龙山地区新生代构造变形特征

基于野外地质调查、地震反射剖面解释和热年代学测试,对柴达木盆地北缘鱼卡—九龙山地区的新生代构造变形特征进行系统分析。结果显示,该地区总体为一个箱状背斜形态,两翼较陡、核部宽缓,马海尕秀背斜和九龙山背斜为箱状背斜两翼受次级断裂影响的次级褶皱,鱼卡本部背斜和鱼卡北部背斜为箱状背斜的宽缓核部发育的次级褶皱。该箱状背斜的形态主要受一些高角度、具有一定右旋走滑分量的逆断层控制,在剖面上形成了明显的正花状构造。结合沉积学研究和碎屑磷灰石裂变径迹分析认为,鱼卡—九龙山地区是一个自新生代早期就开始微弱发育的古隆起构造,使得其上的新生界厚度很薄,其强烈的褶皱变形则发生在晚中新世以后。鱼卡—九龙山古隆起邻近发育中下侏罗统烃源岩的赛南凹陷,具有较好的油气勘探潜力。