Ulansuhai Formation

TypeGeological formation

Unit ofDashuigou Group

PrimaryClaystone, siltstone

Coordinates40°18′N 105°54′E / 40.3°N 105.9°E / 40.3; 105.9

Ulansuhai Formation
Stratigraphic range: Late Cretaceous,  ?Santonian–Campanian PreꞒ Ꞓ O S D C P T J K Pg N (younger than ~92 Ma[1])
Type	Geological formation
Unit of	Dashuigou Group
Lithology
Primary	Claystone, siltstone
Location
Coordinates	40°18′N 105°54′E / 40.3°N 105.9°E / 40.3; 105.9
Approximate paleocoordinates	41°30′N 97°12′E / 41.5°N 97.2°E / 41.5; 97.2
Region	Inner Mongolia
Country	China
Ulansuhai Formation (China) Show map of China Ulansuhai Formation (Inner Mongolia) Show map of Inner Mongolia

The Ulansuhai Formation (simplified Chinese: 乌兰苏海组; traditional Chinese: 烏蘭蘇海組; pinyin: Wūlánsūhǎi Zǔ) is a geological formation in Inner Mongolia, north China. Dinosaur remains are among the fossils that have been recovered from the formation.^[2]

The Ulansuhai Formation has traditionally been considered to date to the Aptian-Albian stages of the Lower Cretaceous, due to similarities between the Ulansuhai fauna and known Aptian formations.^[2] However, radiometric dating done on underlying formations has shown this to be incorrect. Due to the age of underlying rocks, the Ulansuhai Formation cannot be older than the Turonian stage of the Late Cretaceous, about 92 Ma.^[3][4] Evans et al. (2021) suggested that the formation is likely dated to the Santonian-Campanian ages or older, but younger than 92 million years ago.^[1]