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The Huajiying Formation is a geological formation in Hebei, People's Republic of China. Known for its fossils including primitive birds, the age of the formation is uncertain. It may represent an early portion of the Jehol Biota, dating to somewhere in the early Cretaceous or late Jurassic periods. It may correlate with the early Cretaceous Dadianzi Formation and parts of the Yixian Formation, 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 Yixian Formation, 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.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Huajiying Formation」の詳細全文を読む スポンサード リンク
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