Yanan Formation Explained

Yanan Formation
Period:	Middle Jurassic
Type:	Geological formation
Prilithology:	Sandstone, siltstone, mudstone, shale
Otherlithology:	Coal
Subunits:	Y1, Y2, Y3, Y4, Y5
Underlies:	Zhiluo Formation
Overlies:	Fuxian Formation
Thickness:	up to 220m (720feet)
Coordinates:	38.1°N 106.7°W
Paleocoordinates:	42.1°N 111.7°W
Region:	Ningxia, Shaanxi, Inner Mongolia
Country:	China
Extent:	Ordos Basin
Namedfor:	Yan'an

The Yanan Formation, alternatively spelled the Yan'an Formation, 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]

Notes and References

1. Ao. Weihua. Huang. Wenhui. Weng. Chengmin. Xiao. Xiuling. Liu. Dameng. Tang. Xiuyi. Chen. Ping. Zhao. Zhigen. Wan. Huan. January 2012. Coal petrology and genesis of Jurassic coal in the Ordos Basin, China. Geoscience Frontiers. 3. 1. 85–95. 10.1016/j.gsf.2011.09.004. 2012GeoFr...3...85A . 1674-9871. free.
2. 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. 10.1016/j.petrol.2016.06.031. 2016JPSE..145..609W . 0920-4105.
3. 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. 10.1016/j.coal.2012.02.001. 2012IJCG...95....1X . 0166-5162.
4. 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. 10.1080/10420940.2014.985670. 2015Ichno..22....1X . 129509962. 1042-0940.
5. Xu. Xing. Upchurch. Paul. Mannion. Philip D.. Barrett. Paul M.. Regalado-Fernandez. Omar R.. Mo. Jinyou. Ma. Jinfu. Liu. Hongan. 2018-07-24. A new Middle Jurassic diplodocoid suggests an earlier dispersal and diversification of sauropod dinosaurs. Nature Communications. 9. 1. 2700. 10.1038/s41467-018-05128-1. 2041-1723. 6057878. 30042444. 2018NatCo...9.2700X.
6. Dai . Hui . Tan . Chao . Xiong . Can . Ma . Qingyu . Li . Ning . Yu . Haidong . Wei . Zhaoying . Wang . Ping . Yi . Jian . Wei . Guangbiao . You . Hailu . Ren . Xinxin . New macronarian from the Middle Jurassic of Chongqing, China: phylogenetic and biogeographic implications for neosauropod dinosaur evolution . Royal Society Open Science . 2022 . 9 . 11 . 220794 . 10.1098/rsos.220794 . 9627447 . 36340515. 2022RSOS....920794D .