Basement evolution of the Ordos Basin and its constraint on cap rock.Earth Science Frontiers

Since basement evolution has a close relationship with the caprock development, the process of basement evolution of the Ordos Basin and its constraint on caprock can be revealed by comparison between tectonic patterns of caprock series and those of the basement. Our research shows that the basement evolution of Ordos Basin was related to its structure and deformational history, and played an important role in controlling the distortion of the caprock. Under the setting of NS ocean-continent collision in the early Paleozoic, the basement, restricted by its inherited structure, developed NE-trending patterns of apophyses alternating with depressions. Moreover, in the late Paleozoic, a NS-trending center apophysis was superposed on the former NE trend structure patterns by the effect of continent-continent collision. Meanwhile,because the caprock was not thick, its configuration was completely controlled by basement evolution. When it came to the Yanshanian during the Mesozoic, the Ordos Basin underwent EW-trending extrusion, during which the style of the basement remained unaltered. However, the west and east margins of the Ordos Basin experienced distinct vertical movements, with the east margin uplifting and the west margin subsiding. At this time, the cap rocks were well developed and showed characteristics of relatively isolated evolution, although their teeterboard-style of movement was overall under the control of the eastern uplift and western subsidence of the basement.