Detrital Material Source and Paleogeographic Reconstruction of Taiyuan Formation in Western Ordos Basin

Key words: 
• paleogeographic pattern /
• detrital zircon /
• Taiyuan Formation /
• provenance /
• Ordos Basin

Abstract: [Objective] The Taiyuan Formation of Permian system in Ordos Basin has the characteristics of large thickness, wide distribution and rich types of oil and gas resources, showing great exploration potential. At present, the study of this formation is mainly concentrated in the eastern part of the basin, while the exploration and study of Taiyuan Formation in the western part of the basin need to be further discussed due to the complex and variable tectonic pattern and sedimentary evolution.[Methods] The detrital material source, tectonic setting and paleogeographic evolution of Taiyuan Formation in western Ordos Basin are systematically studied by means of outcrop observation, drilling sample collection, detrital zircon U-Pb dating and paleo-flow analysis. [Results] The sediments in the northeastern part of the study area (Group A) are mainly from the Yinshan orogenic belt under the collision-compressional tectonic background, with strong provenances. The delta plain, delta front, tidal sand ridge and tidal sand bar are successively developed in the middle of the basin. The sediments in the northwest (Group B) are derived from the Alxa block under the collisional compression and convergent orogenic tectonic background, and the delta plain, delta front and lagoon-tidal flat develop successively towards the middle of the basin. The sediments in the southern (Group D) area came from the North Qilian and North Qinling tectonic belts under the extension-subduction-collision tectonic environment of the Paleo-Tethyan Ocean. The central paleo-uplift of the Taiyuan Period was slow, the provenance-supply was weak, and the mainly developed barrier island-barrier tidal flat deposits. [Conclusions] The northern part of the study area is characterized by high uplift and strong provenance supply in the context of collision and convergence orogenic structures, and large tide-delta complex system, while the southern part is characterized by weak provenance supply in the context of tensile extension structures, and is dominated by tidal flat and lagoon. This study not only deepens the understanding of the sedimentary system and provenance supply mechanism in the western Ordos Basin, but also provides a new perspective and reference for the reconstruction of the tectono-sedimentary evolution process and paleogeographic pattern in the western Ordos Basin.