LAUSR

Detrital zircon grains were collected from six samples of sedimentary rock from the Middle Jurassic Zhiluo Formation in the western Ordos Basin of China. U–Pb isotopic geochronology data were measured and used to assess the provenance and directions of sediment transport of these grains. Five age populations were recognised amongst the U–Pb age spectra: 2700–2034 Ma, 1999–1426 Ma, 1296–636 Ma, 556–323 Ma, and 315–207 Ma. Each of these groups corresponds to one or several potential sediment sources around the western Ordos Basin. Based on these data and the spatial distribution of the six collected samples, we interpret that the material of the Middle Jurassic Zhiluo Formation in the western Ordos Basin was mainly derived from the northern margin of the North China Craton and the Qilian Orogenic Belt. In addition, the eastern margin of the Alxa Block contributed as a sediment source for certain regions. Detritus was transported via two major supply directions to the western Ordos Basin, and this basin was connected to the Hexi Corridor during the Middle Jurassic. In conclusion, our results are consistent with the closure of Palaeo-ocean and the formation of the orogenic belt.