Yanan Formation

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]

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

Fossil content

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Dinosaurs

Sauropods

Sauropods of the Yanan Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Lingwulong[7]	L. shenqi				A dicraeosaurid sauropod. The attribution to the Yanan Formation was later found to be erroneous, and the species actually comes from the overlying Zhiluo Formation.[6]

Insects

Insects of the Yanan Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Junfengi[8]	J. yulinensis				A campterophlebiid damsel-dragonfly
Kisa[9]	K. fasciata				An archijassid hemipteran
Orthophlebia[10]	O. lini				An orthophlebiid mecopteran
Parasinitsia[11]	P. qingyunensis				A campterophlebiid damsel-dragonfly
Pseudoundacypha[12]	P. yananensis				A thrips
Qibinius[13]	Q. maculatus				A froghopper
Samaroblatta[14]	S. frondoidis				A caloblattinid
Sinagonophlebia[15]	S. yananensis				A paragonophlebiid damsel-dragonfly
Sinolocustopsis[16]	S. brevis				A locustopsid orthopteran
	S. elongatus				A locustopsid orthopteran
Sinopsocus[17]	S. yananensis				A protopsyllidiid hemipteran
Subaphidulum[17]	S. sinica				A protopsyllidiid hemipteran
Yananphasma[18]	Y. chresmodoides				A susumaniid phasmatodean
Yananphilius[19]	Y. peizhuangensis				A sepulcid hymenopteran
Yananthemis[15]	Y. zaoyuanensis				A selenothemistid damsel-dragonfly