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 List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
). It dates to the
Lower Cretaceous
Lower may refer to:
*Lower (surname)
*Lower Township, New Jersey
*Lower Receiver (firearms)
*Lower Wick
Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eight ...
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 ago), a ...
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) b ...
,
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, pp. ...
,
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 ...
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 a ...
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, especiall ...
, 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 fr ...
.
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
*
List of fossil sites
This list of fossil sites is a worldwide list of localities known well for the presence of fossils. Some entries in this list are notable for a single, unique find, while others are notable for the large number of fossils found there. Many of t ...
References
Further reading
*
Geologic formations of Russia
Lower Cretaceous Series of Asia
Cretaceous Russia
Aptian Stage
Paleontology in Russia
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