Major unconformities in the Mesozoic sedimentary sequences in the Kuqa–Tabei region, Tarim Basin, NW China

Abstract

Investigation of major unconformities and large-scale palaeo-uplifts that developed during basin deformation is key in determining the geodynamic setting and hydrocarbon accumulation. Based on the integral analysis of seismic, logging, and outcrop data, the distribution and erosion amounts of Mesozoic major unconformities, the uplifts of the Tabei Uplift and the geodynamic setting in the Kuqa–Tabei region of the Tarim Basin are documented in this study. The Tabei Uplift underwent four stages of uplifts, resulting in four regional angular unconformities and significant changes in palaeo-geomorphology. The deformation occurring at the end of the Permian is characterised by the uplift in the Midwest and the development of an angular unconformity (TT) with maximum erosion thickness of 1200 m. Another deformation occurred at the end of the Triassic, leading to significant uplift of the palaeo-uplift and producing an extensive angular unconformity (TJ) with maximum denudation thickness of 400 m. The end-Jurassic deformation resulted in another uplifting along the palaeo-uplift and generated a regional unconformity (TK) with maximum erosion thickness of 500 m. The Late Cretaceous deformation is characterised mainly by the development of the Wensu Palaeo-uplift in the western margin of the study area. The associated angular unconformity (TE) has a limited distribution mainly along the palaeo-uplift with maximum erosion thickness of 300 m. Four stages of uplifts are attributed to the Palaeo–Tethys oceanic closure; the Qiangtang collision; the Lhasa collision; and the Kohistan collision, respectively. Triangular unconformity belts in the paleo-uplift slope area are favourable for petroleum accumulation.