The Huajiying Formation is a

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...

Hebei Hebei is a Provinces of China, province in North China. It is China's List of Chinese administrative divisions by population, sixth-most populous province, with a population of over 75 million people. Shijiazhuang is the capital city. It bor ...

People's Republic of China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. Known for its

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s including

feathered dinosaur A feathered dinosaur is any species of dinosaur possessing feathers. That includes all species of birds, and in recent decades evidence has accumulated that many non-avian dinosaur species also possessed feathers in some shape or form. The exte ...

s, the age of the formation is uncertain. It may represent an early portion of the

Jehol Biota The Jehol Biota includes all the living organisms – the ecosystem – of northeastern China between 133 and 120 million years ago. This is the Lower Cretaceous ecosystem which left fossils in the Yixian Formation and Jiufotang Formation. These d ...

, dating to somewhere in the early

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

or late

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

periods. It may correlate with the early Cretaceous Dadianzi Formation and parts of the

Yixian Formation The Yixian Formation (; formerly Romanization of Chinese, transcribed as Yihsien Formation or Yixiang Formation) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans the Barremian stage of the Early Cretaceous. I ...

, with an age range between 140 and 122 Ma ago.Wang, 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. It contains the Qiaotou Member, sometimes treated as a distinct formation.

Age and stratigraphy

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

, dated to ~122 Ma ago by Zhou in 2006.Zhou, Z. (2006). "Evolutionary radiation of the Jehol Biota: chronological and ecological perspectives." ''Geological Journal'', 41: 377–393. 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.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.

Paleobiota

The faunal lists below are based on a survey of the Huajiying Formation by Jin Fan and colleagues in 2008, unless otherwise noted.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.

Theropods

Pterosaurs

Fishes

Invertebrates

References

{{reflist Geologic formations of China Lower Cretaceous Series of Asia Cretaceous China Lagerstätten Fossiliferous stratigraphic units of Asia Paleontology in Hebei