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The study of tectonic, provenance, and paleogeomorphologic systems is important for defining the basin evolution and it is also the basis for the accurate evaluation of oil and gas potential of a basin. The provenance and paleogeomorphology of the western Ordos Basin and the Hexi Corridor in the southwestern North China Craton(sw-NCC) have long been debated. In this study, detrital zircon geochronology, petrography and geochemistry methods are used to analyse the evolution of provenance and paleogeomorphology in the sw-NCC during the Middle–Late Triassic, and the provenance and paleogeomorphic relationships with tectonic events are discussed. The U–Pb detrital zircon geochronology of the Yaoshan samples in the western Ordos Basin are clear and consistent, and shows that there are three major age populations, 2700–2200 Ma, 2150–1650 Ma and 450–220 Ma. While the age spectrums of the samples from different formations in the Hexi Corridor are complex, showing significant differences. The whole results imply that the Hexi Corridor and the west margin of the Ordos Basin had a unified source during the Middle Triassic, which is the western NCC. However, in the Late Triassic, the sediment of the Hexi Corridor was mainly from the Qilian–Qaidam Terrane while the source of the western Ordos Basin remained unchanged. Besides the provenance analysis, the stratigraphic correlation, petrology and geochemistry analyses also support that the Hexi Corridor was temporarily connected with the Ordos Basin during the Middle Triassic but was separated from the Ordos Basin by a small-scale, underwater paleo-uplift during the Late Triassic. The evolution of the provenance and paleogeomorphology in the southwestern Ordos Basin was related to the closure of the shallow shelf of the Paleo-Tethys Ocean. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic Jixian System (1.6–1.4 Ga) in the Luonan area, southern margin of the North China Craton (NCC), is characterized by complete development, continuous sedimentation and a low degree of structural deformation, resulting in well-preserved palaeontological and paleoenvironmental records. Carbon, oxygen and strontium isotopes of 382 dolostone samples from the Jixian System in Xiong'er Rift, southern margin of the NCC are analysed for the restoration of paleoenvironment and stratigraphic correlation. The results show that the δ13C values of these samples mainly concentrate between −1.8‰ and 2.0‰, and the values can be divided into three segments. The δ18O values are mainly between −6.5‰ and −3.5‰, with frequent fluctuations and weak regularity. The 87Sr/86Sr ratio ranges from 0.7051 to 0.7139, with an average value of 0.7085. Its fluctuations have certain regularity and are negatively correlated with the carbon isotopes, indicating that the sea-level changes during the Jixian period in the southern margin of the NCC. The carbon isotope curve of the samples from the study section is very similar to those of the Xiong'er Rift and the Yanliao Rift of the NCC. The −3.2‰ δ13C negative excursion in the middle and upper parts of the Xunjiansi Formation corresponds to the δ13C negative excursion from the top of the Wumishan Formation to the bottom of the Tieling Formation in the Yanliao Rift. Combined with previous research data, the Jixian System that deposited in the Xiong'er Rift and the Yanliao Rift can be approximately correlated with each other. In addition, the carbon isotope data obtained from this study is comparable to global carbon isotope values during the same period. The rise and oscillation of carbon and strontium isotope values during this period may be a response to the break-up of the Colombian supercontinent. [ABSTRACT FROM AUTHOR]