Karabastau Formation

Karabastau Formation
Stratigraphic range: Middle Jurassic - Late Jurassic Callovian–Kimmeridgian PreꞒ Ꞓ O S D C P T J K Pg N
Specimen of the salamander Karaurus sharovi
Type	Geological formation
Area	Karatau Mountains
Thickness	26 m (85 ft) exposed
Lithology
Primary	Claystone dolomite,
Other	Sandstone, conglomerate
Location
Region	Central Asia
Country	Kazakhstan

The Karabastau Formation (Kazakh: Qarabastaý svıtasy) is a geological formation and lagerstätte in the Karatau Mountains of southern Kazakhstan whose strata date to the Middle to Late Jurassic. It is an important locality for insect fossils that has been studied since the early 20th century, alongside the rarer remains of vertebrates, including pterosaurs, salamanders, lizards and crocodiles.^[1][2]

The primary lithology consists of 1 mm thick varve laminations of claystone, with a dark part and a light dolomitic part, which probably correspond to a wet and dry season respectively, alongside rare, several cm thick sandstone interbeds. These were deposited within an ancient freshwater paleolake, that given the number of laminations has been suggested to have existed for over 150,000 years. The top of the formation shows the laminations becoming wavy, likely as a result of microbial interactions, and the top of the formation is capped by a conglomerate predominantly composed of black Carboniferous limestone pebbles.^[2]

The Karabastau Formation was first discovered in 1921 by Soviet geologists, and was declared a protected paleontological reserve in 1924.^[2]

Genus	Species	County	Member	Abundance	Notes	Images
Batrachognathus	B. volans			2 specimens	An Anurognathid Pterosaur.
Karatausuchus	K. sharovi				An Atoposaurid Crocodylomorph.
Karaurus	K. sharovi				stem-group salamander.
Praeornis	P. sharovi			2 specimens	Proto-Feather
Sharovisaurus	S. karatauensis				A Paramacellodid lizard
Sordes	S. pilosus			8 specimens	A Pterodactylomorph Pterosaur.
Yaxartemys	Y. longicauda				Turtle, possibly belongs to Xinjiangchelyidae
Morrolepis	M. aniscowitchi			346 specimens	Coccolepidid fish[3]
Pteroniscus	P. turkestanensis				Palaeonisciform fish, closely related to Uighuroniscidae and Daqingshaniscus.[3]
Spherosteus	S. scharovi				Peipiaosteid fish, related to sturgeons and paddlefish

Hundreds of species of insects are known from several localities within the formation, primarily Karatau-Mikhailovka^{[4][5][6][7][8][9][10][11][12][13]}

• List of pterosaur-bearing stratigraphic units
• List of fossiliferous stratigraphic units in Kazakhstan