Relationship between orogenic belt uplift and non-equilibrium subsidence basins: a case study of Chang 7 and Chang 6 oil reservoirs in Longdong area, Ordos Basin

The influence the Qinling Orogenic Belt uplift on provenance to the Chang 7 and Chang 6 oil reservoirs in the Longdong area of the Ordos Basin was analyzed. Outcrop and core observation and zircon U-Pb dating were used to characterize the temporal and spatial distributions of deposits such as tuff interlayers, gravity flows and seismites. The relationship between orogenic belt uplift and deposits were discussed. The "scissor-like" subduction closure of the Qinling Orogenic Belt from east to west was the driving force for the continuous migration of the depositional center of the basin, and the largest deep depression was formed in the southwestern part of the lake basin during the Chang 7 period. The intrusive "S-type granite" associated with the uplift of the Western Qinling provided a material source for the deep depression area in the southwest. Deposits are widely distributed in the deep depression area, among which the tuff interlayer is homologous to the intrusive magmatic rocks of the West Qinling, and the thickness gradually decreases from south to north. Turbidity current and some sandy clastic flow deposits were developed in the southwestern slope break belt of the deep depression area, while sandy clastic flow and some turbidity flow and argillaceous clastic flow deposits developed in the northeastern part of the depression area. From the southwest to the northeast of the basin, the deformation frequency, magnitude and scale of seismic core gradually decreased, indicating that the source is from the vicinity of the West Qinling. Therefore, the uplift of the Qinling Orogenic Belt has a good spatio-temporal coupling relationship with the non-equilibrium settlement and sedimentary response characteristics of the Ordos Basin.