Tiaojishan Formation
| Tiaojishan Formation | |
|---|---|
| Stratigraphic range: Bathonian-Oxfordian ~ | |
Exposure of the Tiaojishan Formation at Nanshimenzi Village, Qinglong Manchu Autonomous County, Hebei Province, with red arrow pointing to fossiliferous beds | |
| Type | Geological formation |
| Underlies | Tuchengzi Formation, Houcheng Formation |
| Overlies | Haifanggou Formation |
| Thickness | 2,420 m (7,940 ft) |
| Lithology | |
| Primary | Andesite |
| Other | Sandstone, shale, tuff, coal |
| Location | |
| Coordinates | 41°18′N 119°12′E / 41.3°N 119.2°E |
| Approximate paleocoordinates | 43°00′N 123°06′E / 43.0°N 123.1°E |
| Region | Hebei, Inner Mongolia, & Liaoning |
| Country | China |
| Extent | Yanshan Belt |
The Tiaojishan Formation is a geological formation in Hebei and Liaoning, People's Republic of China, dating to the middle-late Jurassic period (Bathonian-Oxfordian stages). It is known for its exceptionally preserved fossils, including those of plants, insects and vertebrates. It is made up mainly of pyroclastic rock interspersed with basic volcanic and sedimentary rocks. Previously, the Tiaojishan Formation was grouped together with the underlying Haifanggou Formation (also known as the Jiulongshan Formation) as a single "Lanqi Formation." The Tiaojishan Formation forms a key part of the Yanliao Biota assemblage, alongside the Haifanggou Formation.