| Yanan Formation | |
|---|---|
| Stratigraphic range: Toarcian–Bajocian
| |
| 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°06′N 106°42′E / 38.1°N 106.7°E / 38.1; 106.7 |
| Approximate paleocoordinates | 42°06′N 111°42′E / 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)  Yanan Formation (Ningxia) Show map of Ningxia | |
The Yanan Formation, alternatively spelled the Yan'an Formation (Chinese: 延安组), is a geological formationinChina, it is also alternatively considered a group. The age of the formation is uncertain, with estimates ranging from ToarciantoBajocian. 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]
