There are significant differences in the characteristics of sedimentary rock and coal seams between the upper and lower members of the Middle Jurassic Xiahuayuan Formation in Yuxian County, Hebei Province, China. These two members represent sedimentary products in different tectonic and palaeogeographic conditions, indicating tectonic movements between them. There is an unconformable contact between the upper and lower members of this formation and the boundary between them should be placed at the base of the mottled rock bed.