The Zaza Formation is a geological formation located in

Buryatia Buryatia, officially the Republic of Buryatia (russian: Республика Бурятия, r=Respublika Buryatiya, p=rʲɪsˈpublʲɪkə bʊˈrʲætʲɪjə; bua, Буряад Улас, Buryaad Ulas, , mn, Буриад Улс, Buriad Uls), is ...

(

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-ei ...

). It dates to the

Lower Cretaceous Lower may refer to: * Lower (surname) * Lower Township, New Jersey *Lower Receiver (firearms) * Lower Wick Gloucestershire, England See also *Nizhny Nizhny (russian: Ни́жний; masculine), Nizhnyaya (; feminine), or Nizhneye (russian: Н� ...

period. It is

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ag ...

in age and consists of

sandstones Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

siltstones Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

marls Marl is an earthy material rich in carbonate minerals, clays, and silt. When hardened into rock, this becomes marlstone. It is formed in marine or freshwater environments, often through the activities of algae. Marl makes up the lower part o ...

and

bituminous Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...

shales Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especially ...

, deposited in a stratified lake. It is situated on a large granite plateau in the NE of Buryatia.Zherikhin, V.V., Mostovski, M.B., Vrsansky, P., Blagoderov, V.A. and Lukashevich, E.D. 1999
The unique Lower Cretaceous locality of Baissa and other contemporaneous insect-bearing sites in North and West Transbaikalia
''Proceedings of the First Palaeoentomological Conference, Moscow, 1998''. Bratislava: Amba Projects, pp. 185-192. The formation is known for its numerous compression fossils of many varieties of insect found predominantly at the Baissa locality, located on the banks of the

Vitim River The Vitim (russian: Витим; evn, Витым, ; sah, Виитим, ; Buryat and mn, Витим, ''Vitim'') is a major tributary of the Lena. Its source is east of Lake Baikal, at the confluence of rivers Vitimkan from the west and China f ...

. Insects are found in multiple beds throughout the succession, predominantly in the finer grained facies, the preservation of insect fossils is variable between beds, with good preservation in marl and poor preservation in shale beds.

See also

References

Further reading