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The Yanan Formation, alternatively spelled the Yan'an Formation (Chinese:延安组), is a geological formation in China, it is also alternatively considered a group. The age of the formation is uncertain, with estimates ranging from Toarcian to Bajocian. It is divided up into 5 members, with the designation of Y1 through Y5. Y2, Y3 and Y4 are predominantly dark shales, while Y1 and Y5 are composed of sandstones, coal beds[1] and interbedded mudstones. The depositional environment at the time was when the Ordos Basin formed a large inland lake, surrounded by floodplains. The dark shales have been explored for the potential of producing shale gas.[2] The coal has also been explored for the production of coalbed methane.[3] The formation is also notable for its fossil content, with dinosaur footprints having been found in the formation.[4] The dinosaur Lingwulong was formerly thought to have been found in this formation,[5] but the strata was later attributed to the overlying Zhiluo Formation.[6]
A diplodocoidsauropod. The attribution to the Yanan Formation was later found to be erroneous, and the species actually comes from the overlying Zhiluo Formation.[6]
↑Wang, Dong-dong; Shao, Long-yi; LI, Zhi-xue; LI, Ming-pei; Lv, Dawei; Liu, Haiyan (September 2016). "Hydrocarbon generation characteristics, reserving performance and preservation conditions of continental coal measure shale gas: A case study of Mid-Jurassic shale gas in the Yan'an Formation, Ordos Basin". Journal of Petroleum Science and Engineering. 145: 609–628. Bibcode:2016JPSE..145..609W. doi:10.1016/j.petrol.2016.06.031. ISSN0920-4105.
↑Xu, H.; Tang, D.Z.; Liu, D.M.; Tang, S.H.; Yang, F.; Chen, X.Z.; He, W.; Deng, C.M. (June 2012). "Study on coalbed methane accumulation characteristics and favorable areas in the Binchang area, southwestern Ordos Basin, China". International Journal of Coal Geology. 95: 1–11. Bibcode:2012IJCG...95....1X. doi:10.1016/j.coal.2012.02.001. ISSN0166-5162.
↑Xing, Lida; Lockley, Martin G.; Tang, Yonggang; Klein, Hendrik; Zhang, Jianping; Persons, W. Scott; Dai, Hui; Ye, Yong (2015-01-02). "Theropod and Ornithischian Footprints from the Middle Jurassic Yanan Formation of Zizhou County, Shaanxi, China". Ichnos. 22 (1): 1–11. Bibcode:2015Ichno..22....1X. doi:10.1080/10420940.2014.985670. ISSN1042-0940. S2CID129509962.
↑Zheng, D.; Dong, C.; Wang, H.; Ye, Y.; Wang, B.; Chang, S.-C.; Zhang, H. (2017). "The first damsel-dragonfly (Odonata: Isophlebioidea: Campterophlebiidae) from the Middle Jurassic of Shaanxi Province, northwestern China". Alcheringa: An Australasian Journal of Palaeontology. 41 (4): 509–513. doi:10.1080/03115518.2017.1318170. S2CID133806124.
↑Fu, Y.; Xu, M.; Gao, J.; Huang, D. (2023). "The Archijassidae from the Jurassic of China (Hemiptera, Cicadomorpha, Membracoidea) and its palaeoecological significance". Historical Biology: An International Journal of Paleobiology. 36 (10): 2233–2238. doi:10.1080/08912963.2023.2250109. S2CID261636256.
↑Lian, X.-N.; Cai, C.-Y.; Feng, Z.; Huang, D.-Y. (2024). "New orthophlebiid mecopteran from the Middle Jurassic Yan'an Formation, China". Journal of Insect Biodiversity. 60 (1): 47–54. doi:10.12976/jib/2024.60.1.8.
↑Fu, Y.; Huang, D. (2020). "A new fossil cercopoid from the middle Jurassic Ordos and Jiyuan basins, northern China (Hemiptera, Cicadomorpha)". Historical Biology: An International Journal of Paleobiology. 33 (10): 2025–2030. doi:10.1080/08912963.2020.1765167. S2CID219747247.
↑Liang, Junhui; Shih, Chungkun; Ren, Dong (2019), "Blattaria – Cockroaches", in Ren, Dong; Shih, Chung Kun; Gao, Taiping; Yao, Yunzhi; Wang, Yongjie (eds.), Rhythms of Insect Evolution: Evidence from the Jurassic and Cretaceous in Northern China, pp.91–112, doi:10.1002/9781119427957.ch7, ISBN978-1-119-42795-7
12Nel, A.; Xu, M.; Wang, Y.; Song, X.; Gao, J.; Ji, G.; Huang, D. (2024). "New Chinese Jurassic damsel-dragonflies of the families Paragonophlebiidae, Selenothemistidae and Isophlebiidae (Odonata, Epiproctophora) from the Jurassic Ordos Basin of NW China". Geobios. 87: 37–44. doi:10.1016/j.geobios.2024.08.014.
12Xu, M.-M.; Hakim, M.; Huang, D.-Y. (2023). "New Jurassic protopsyllidiids from the Yan'an Formation, North China (Insecta: Hemiptera)". Palaeoentomology. 6 (5): 542–548. doi:10.11646/palaeoentomology.6.5.13. S2CID264597972.
↑Guo, Q.-M.; Xu, C.-P.; Nel, A.; Peng, A.-C.; Wen, Z.-G.; Li, T.; Fang, R.; Zheng, D.-R. (2025). "A new genus and species of Susumaniidae (Insecta: Phasmatodea) from the Middle Jurassic of Shaanxi Province, Northwest China". Palaeoworld. 34 (5) 200942. doi:10.1016/j.palwor.2025.200942.
↑Jouault, C. (2024). "A new parapamphiliin wasp (Hymenoptera: Sepulcidae) from the Middle Jurassic Yan'an Formation, China". Journal of Insect Biodiversity. 60 (1): 83–88. doi:10.12976/jib/2024.60.1.12.
↑Song, Z.-H.; Wang, Z.-E.; Wang, H.; Li, X.; Wu, J.-Y.; Ding, S.-T. (2026). "First macrofossil record of Selaginellites from the Jurassic of northwestern China". Review of Palaeobotany and Palynology. 348 105534. Bibcode:2026RPaPa.34805534S. doi:10.1016/j.revpalbo.2026.105534.