Prototypical basin reconstruction and evolutionary models for the Precambrian of the Qinshui Basin, North China craton

Abstract

The thick Precambrian strata in the Qinshui Basin (QB) have high potential for hydrocarbon exploration. Tectonic evolution restoration and prototype basin reconstruction are key to hydrocarbon exploration and evaluation for Precambrian strata. We studied the 2D/3D seismic data and Precambrian field outcrops of the QB to elucidate its geological attributes, major regional unconformities, tectonostratigraphic framework, tectonic evolution and prototype basin. The Precambrian strata of the QB are the sedimentary products of the continuous transgression from south to north and are more appropriately attributed to the Xiong'er Aulacogen in the Changchengian and Jixian periods. We identified six regional unconformities: the Archean or Palaeoproterozoic/Xiong'er Group, the Xiong'er Group/Chy, Chc/Chl, Chl/Jxl, the Jxl/Cambrian System, and the Ordovician/Carboniferous. Seven tectonostratigraphic units can be delineated: the Archean–Palaeoproterozoic, Xiong'er Group, Yunmengshan–Cuizhuang, Luoyukou, Jixian, Cambrian–Ordovician, and Carboniferous–Triassic tectonostratigraphic units. The tectonic evolution was divided into seven stages: the formation and evolution of the basement (∼1800 Ma), the synrift stage in the Xiong'er period (1800–1720 Ma), the postrift stage in the Yunmengshan–Luoyukou period (1720–1600 Ma), the passive continental margin basin stage in the Jixian period (1600–1400 Ma), the marine craton stage during the Cambrian–Ordovician (542–440 Ma), the marine–continental transitional–continental craton stage during the Carboniferous–Triassic (316–200 Ma), and the intense deformation stage (200–0 Ma). Three stages of prototype basin models of the Precambrian in the QB have been reconstructed: (1) In the synrift basin model, numerous normal faults have developed, and the section shows a symmetrical composite graben. The topography in the south is low, that in the north is high, and the northeast and northwest areas are palaeo-uplifted. A set of volcanic rocks with coarse-grained clasts was deposited. (2) In the postrift basin model, the fault activity weakened, and the depositional range became larger than that of the synrift stage, and a set of marine clastic–carbonate rocks was deposited showing a gradual coarsening–upwards trend. (3) In the passive continental margin basin model, the fault became almost inactive, the topography was low in the southeast and high in the northwest, and the depositional area was more widespread, resulting in a set of marine carbonates. These results contribute to a better understanding of the break-up process of the Columbia supercontinent and the Precambrian evolution of the North China Craton (NCC) and can be used to predict the distributions of source rocks and hydrocarbons.