Yanan Formation

Yanan Formation Stratigraphic range: Early to Middle Jurassic ~174 Ma PreЄ Є O S D C P T J K Pg N ↓
Type	Geological formation
Unit of	Ordos Basin
Sub-units	Y1, Y2, Y3, Y4, Y5
Underlies	Zhiluo Formation
Overlies	Fuxian Formation
Thickness	up to 220 metres (720 ft)
Lithology
Primary	Sandstone, Siltstone, Mudstone, Shale
Other	Coal
Location
Region	East Asia
Country	China
Extent	Ningxia, Shaanxi

The Yanan Formation, alternatively spelled the Yan'an Formation is a geological formation in China. 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^[4] and the remains of the sauropod Lingwulong^[5] having been found in the formation.

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