The Ulaanoosh Formation, formerly Baruunbayan Formation, is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

in the Ömnögovi Province of southern

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...

. The formation dates to the Albian to

Cenomanian The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the s ...

stages of the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

. The Ulaanoosh Formation has provided fossils of

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...

s and dinosaur eggs assigned to '' Parafaveoloolithus sp.''. In

2020 2020 was heavily defined by the COVID-19 pandemic, which led to global Social impact of the COVID-19 pandemic, social and Economic impact of the COVID-19 pandemic, economic disruption, mass cancellations and postponements of events, COVID- ...

, the neoceratopsian ''

Beg tse ''Beg'' (after the Himalayan war deity Beg-tse) is a genus of neoceratopsian dinosaur from the early Cretaceous period of Mongolia. The genus contains a single species, ''Beg tse'', known from a partial skull and very fragmentary postcrania. '' ...

'' was described from the

alluvial Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluv ...

sandstone 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) ...

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...

s and conglomerates of the formation.

Description

The Ulaanoosh Formation was formerly considered to be the Baruunbayan Formation (or Baruunbayan Svita in Russian or Mongolian),Baruunbayan Formation
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals ...

.org first documented by the Soviet-Mongolian Paleontological Expeditions between 1946 and 1949. These beds are now considered to be part of the Ulaanoosh Formation. Shuvalov (1982) recognized the red beds at Baruunbayan based on exposures near mountains adjacent to the towns of Baruunbayan and Zuunbayan. Later, the Baruunbayan Svita was more thoroughly studied during a large geological mapping project carried out in the same area by a variety of studies. Due to insufficient representation (only partial sections are exposed at these localities), Badamgarav et al. in 1995 proposed that the Ulaanoosh Formation represents a complete section of red beds in the Baruunbayan area based on drill logs. The Ulaanoosh Formation is distributed in the areas of Ulaanoosh, Alguu Ulaan Tsav, Baruunbayan, and Zuunbayan. The age of the Ulaanoosh Formation ranges from late Early to early Late Cretaceous ( Albian-

) based on vertebrate and invertebrate fossils such as dinosaurs, dinosaur eggs, molluscs, ostracods, and turtles.Yu et al., 2020, p.2 The Ulaanoosh Formation is composed of two members: a lower and an upper. The lower member (Aptian to Albian) comprises white-colored

s, fine-grained conglomerates, bright gray colored, carbonate-rich

s, yellowish fine-grained sandstones with carbonate concretions and gray colored conglomerates preserving invertebrate fossils. The upper member is largely composed of reddish colored, fine to medium grained

s, fine-medium grained conglomerates, and a

breccia Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of di ...

layer in the base. The upper member of the formation preserved fragmentary sauropods and dinosaur eggs ''

Faveoloolithus ''Faveoolithus'' is an oogenus of dinosaur egg. The oogenus contains two oospecies, ''F. ningxiaensis'' and ''F. zhangi''.Early Early may refer to: History * The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.: ** Early Christianity ** Early modern Europe Places in the United States * Early, Iowa * Early, Texas * Early ...

and

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

(~100.5 Ma).

Fossil content

The following fossils have been reported from the formation:

References

Bibliography

* * * * * * {{CC-notice, cc=by4, url=https://www.nature.com/articles/s42003-020-01222-7, author(s)=Congyu Yu, Albert Prieto-Marquez, Tsogtbaatar Chinzorig, Zorigt Badamkhatan & Mark Norell Geologic formations of Mongolia Cretaceous System of Asia Cretaceous Mongolia Albian Stage Cenomanian Stage Conglomerate formations Mudstone formations Sandstone formations Alluvial deposits Ooliferous formations Fossiliferous stratigraphic units of Asia Paleontology in Mongolia Formations

Description

Fossil content

See also

References

Bibliography