Ukureyskaya Formation

The Ukureyskaya Formation, also referred to as the Ukurey Formation, is a geological formation in Zabaykalsky Krai, part of the Russian Far East. It is made up of Middle Jurassic and Late Jurassic layers.^[1] It covers large areas around Kulinda.^[2]

Ukureyskaya Formation
Stratigraphic range: Bajocian–Tithonian, 169–144 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Sub-units	Lower, Middle and Upper subformations
Underlies	Utanskaya Formation
Overlies	Kulindinskaya Formation
Thickness	Several hundred metres
Lithology
Primary	Sandstone, siltstone, tuffite
Other	Mudstone
Location
Coordinates	52.5°N 116.7°E / 52.5; 116.7
Approximate paleocoordinates	58.0°N 117.2°E / 58.0; 117.2
Region	Zabaykalsky Krai
Country	Russia
Extent	Zabaykalsky Krai
Ukureyskaya Formation (Russia) Show map of Russia Ukureyskaya Formation (Zabaykalsky Krai) Show map of Zabaykalsky Krai

History

The Ukureyskaya Formation was mentioned by Sinitsa & Starukhina (1986),^[3] and was first discovered by Sofia M. Sinitsa and her team from the Russian Academy of Sciences before being excavated in 2010 by a group of Russian and Belgian palaeontologists;^[4] during this time, the holotype of Kulindadromeus zabaikalicus was discovered.^[5] Excavations wrapped up in 2013 or 2014.^[6]

Description

The volcanic ash layers of the Ukureyskaya Formation form a Konservat-Lagerstätte with an exceptional preservation,^[1] and it likely represents a nearshore lacustrine or estuarine-deltaic environment similar to the Yixian Formation.^[2]

In total, two bone beds were identified during the excavations that took place between 2010 and 2013/14;^[6] Bonebed 4 is older than Bonebed 3.

Age

Sinitsa & Starukhina (1986) and Sinitsa (2011) suggested that the Ukureyskaya Formation dated to the Late Jurassic-Early Cretaceous.^[3][4]

Godefroit et al. (2014) and Alivanov & Saveliev (2014) have suggested that as a whole, the Ukureyskaya Formation dates to the Bajocian-Tithonian,^[5][7] while more recent dating work by Cincotta et al. (2019) suggests that the layers containing the remains of Kulindadromeus are Bathonian in age.^[8]

Paleofauna

Paleofauna of the Ukureyska Formation

Genus	Species	Location	Stratigraphic position	Material	Notes	Image
Crustacea[2]	Indeterminate[2]	Kulinda[2]	"Indeterminate remains"[2]
Insecta[5]	Indeterminate[5]	Kulinda[5]			Represented by multiple species.[5]
Kulindadromeus[5][7]	K. zabaikalicus[5][7]	Kulinda[5]	"Base of the Ukureyska Formation"[5]	"Hundreds of disarticulated skeletons including six skulls"[5]	Synonyms include Daurosaurus olovus and Lepidocheirosaurus natalis.[9]
Ornithopoda[2]	Indeterminate[2]	Kulinda[2]		"Indeterminate remains"[2]	Represents an unnamed genus that is distinct from Kulindadromeus.[2]
Theropoda[2]	Indeterminate[2]	Kulinda[2]		"Single tooth"[2]	Based on undiagnostic remains.[2]