Characteristics of the Gaojiapu anticline in the eastern Ordos Basin and its implications for the Lüliang Uplift activity

The Gaojiapu anticline in the eastern Ordos Basin offers critical insights into the coupling relationship between intra-basin and basin-margin tectonic deformation. Based on recent drilling and 3D seismic data, this study accurately characterizes the geometry of the anticline, applies the area-depth method to estimate its shortening amount and detachment depth, and investigates the relationship between the thickness of incompetent layers and anticline. Furthermore, the genetic connection between the anticline and the Yanshanian activity of the Lüliang Uplift at the basin margin is discussed. The results indicate that: 1) the Gaojiapu anticline is a nearly north-south-striking long-axis structure, with a long-to-short axis ratio ranging from 5∶1 to 14∶1. It developed from the basement upward to the shallow Yanchang Formation. Above the Ma-3 member, which is a set of salt layer, the anticline exhibits a relatively broad and gentle form, whereas beneath the salt, it comprises two tight anticlinal zones. Although the spatial distribution of the anticline above and below the salt shows strong inheritance, the structural high points have shifted. 2) The anticline is a detachment fold formed under compression along a basal detachment surface located between -5 km and -5.6 km in elevation, with a stratigraphic shortening of approximately 120~190 m. This deformation prompted the passive migration of salt within the Ma-3 member toward the anticlinal core, as indicated by the correspondence between the maximum salt thickness and the anticlinal development area. 3) The Gaojiapu anticline primarily developed during the Yanshanian Period as a far-field response to eastward compression from the Lüliang Uplift along the basement. Deformation was localized within a weak zone in the eastern part of the basin, where the structural style transitions from a wedge thrust to a detachment fold. This study provides valuable insights for basin-mountain coupling analysis in the eastern Ordos Basin and supports further evaluation of hydrocarbon accumulation and enrichment in subsalt reservoirs.