Yanan Formation

The Yanan Formation, alternatively spelled the Yan'an Formation (simplified 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[4] and the remains of the sauropod Lingwulong[5] having been found in the formation.

Yanan Formation Stratigraphic range: Toarcian–Bajocian PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
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
Coordinates	38.1°N 106.7°E / 38.1; 106.7
Approximate paleocoordinates	42.1°N 111.7°E / 42.1; 111.7
Region	Ningxia, Shaanxi, Inner Mongolia
Country	China
Extent	Ordos Basin
Type section
Named for	Yan'an
Yanan Formation (China) Show map of China Yanan Formation (Ningxia) Show map of Ningxia