Tiaojishan Formation

Tiaojishan Formation
Stratigraphic range: Bathonian-Oxfordian ~165–153 Ma PreꞒ Ꞓ O S D C P T J K Pg N
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 / 41.3; 119.2
Approximate paleocoordinates	43°00′N 123°06′E / 43.0°N 123.1°E / 43.0; 123.1
Region	Hebei, Inner Mongolia, & Liaoning
Country	China
Extent	Yanshan Belt
Tiaojishan Formation (China) Show map of China Tiaojishan Formation (Liaoning) Show map of Liaoning

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."^[1] The Tiaojishan Formation forms a key part of the Yanliao Biota assemblage, alongside the Haifanggou Formation.