The Huajiying Formation contains the following members, in order from youngest to oldest:
5th Volcanic Member
Guohedao Sedimentary Member
4th Volcanic Member
Nianzigou Sedimentary Member
3rd Volcanic Member
Qiaotou Sedimentary Member
2nd Volcanic Member
Sichakou Sedimentary Member
1st Volcanic Member
The age of the formation is uncertain. Ji and colleagues suggested in 2008 that the Qiaotou Member correlates with the Dawangzhangzi bed of the Yixian Formation, dated to ~122 Ma ago by Zhou in 2006.[2] Ji et al. also suggested that the lower Sichakou Member correlates with the Dadianzi Formation, dated to 140 Ma ago by Tian and colleagues in 2003.[3]
Paleobiota
The faunal lists below are based on a survey of the Huajiying Formation by Jin Fan and colleagues in 2008, unless otherwise noted.[4]
^ abWang, X., O’Connor, J.K., Zhao, B., Chiappe, L.M., Gao, C. and Cheng, X. (2010). "New species of Enantiornithes (Aves: Ornithothoraces) from the Qiaotou Formation in Northern Hebei, China." Acta Geologica Sinica, 84(2): 247-256.
^Zhou, Z. (2006). "Evolutionary radiation of the Jehol Biota: chronological and ecological perspectives." Geological Journal, 41: 377–393.
^Tian, S.G., Liu, Y.Q., Li, P.X., Pang, Q. and Niu, S. (2003). "Sequence stratigraphy of Jurassic-Cretaceous boundary strata in Luanping, Northern Hebei, China." Science in China Series D: Earth Sciences, 47(7): 607―617.
^Jin, F., Zhang, F.C., Li, Z.H., Zhang, J.Y., Li, C. and Zhou, Z.H. (2008). "On the horizon of Protopteryx and the early vertebrate fossil assemblages of the Jehol Biota." Chinese Science Bulletin, 53(18): 2820-2827.
^Zhou, Chang-Fu; Zhu, Ziheng; Chen, Jianye (2022-05-22). "First pterosaur from the Early Cretaceous Huajiying Formation of the Jehol Biota, northern Hebei Province, China: insights on the pedal diversity of Pterodactyloidea". Historical Biology. 35 (7): 1129–1135. doi:10.1080/08912963.2022.2079085. ISSN0891-2963.