The Madygen Formation (

Russian Russian(s) refers to anything related to Russia, including: *Russians (, ''russkiye''), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *Rossiyane (), Russian language term for all citizens and peo ...

: Madygen Svita) is a

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...

(

Carnian The Carnian (less commonly, Karnian) is the lowermost stage of the Upper Triassic Series (or earliest age of the Late Triassic Epoch). It lasted from 237 to 227 million years ago (Ma). The Carnian is preceded by the Ladinian and is followe ...

)

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 ...

and

Lagerstätte A Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These for ...

in the

Batken Batken (also called Batkent) is a town in southwestern Kyrgyzstan, on the southern fringe of the Fergana Valley. It is the administrative seat of Batken Region. Since 2000, it is a city of regional significance, i.e. not part of a district. Howeve ...

and

Osh Region Osh Region ( ky, Ош облусу, translit=Osh oblusu; russian: Ошская область, Oshskaya oblast) is a region (''oblast'') of Kyrgyzstan. Its capital is Osh, which is not part of the region. It is bounded by (clockwise) Jalal-Abad R ...

s of western

Kyrgyzstan Kyrgyzstan,, pronounced or the Kyrgyz Republic, is a landlocked country in Central Asia. Kyrgyzstan is bordered by Kazakhstan to the north, Uzbekistan to the west, Tajikistan to the south, and the People's Republic of China to the ea ...

, with minor

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficia ...

s in neighboring Tajikistan and Uzbekistan. The conglomerates,

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 ...

s and mudstones of the thick formation were deposited in terrestrial

lacustrine A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...

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. Al ...

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluv ...

and deltaic

environments Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

. The formation, extending across the

Fergana Valley The Fergana Valley (; ; ) in Central Asia lies mainly in eastern Uzbekistan, but also extends into southern Kyrgyzstan and northern Tajikistan. Divided into three republics of the former Soviet Union, the valley is ethnically diverse and in the ...

and

Fergana Range The Fergana Range ( ky, Фергана тоо кыркасы, ''Ferğana tó qırqası/Fergana too kyrkasy'', فەرعانا توو قىرقاسى), also known as Ferganskiy Khrebet (Феранский Хребет) ''Ferganskij Hrebet'' in Russi ...

, is unique for Central Asia, as it represents one of the few known continental deposits and the Madygen Formation is renowned for the preservation of more than 20,000 fossil insects, making it one of the richest Triassic Lagerstätten in the world. Other vertebrate fossils as fish, amphibians, reptiles and synapsids have been recovered from the formation too, as well as minor fossil flora. The lake sediments of the Lagerstätte provided fossil

cartilaginous fishes Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue. ...

and their egg capsules and unusual Triassic reptiles like ''

Sharovipteryx ''Sharovipteryx'' ("Sharov's wing", known until 1981 as ''Podopteryx'', "foot wing"), is a genus of early gliding reptiles containing the single species ''Sharovipteryx mirabilis''. It is known from a single fossil and is the only glider with a m ...

'' and '' Longisquama''.Fischer et al., 2011Unwin et al., 2003, pp.177-186 The wide diversity of insect fossils was first discovered in the 1960s and first described by Russian paleontologist Aleksandr Sharov, with a notable example being '' Gigatitan''.Shcherbakov, 2008

Description

The Madygen Formation is a Fischer et al., 2018, p.25 thick succession of predominantly siliciclastic rocks accumulated in a tectonically induced basin, covering parts of the

and

of Kyrgyzstan with minor outcrops in

Tajikistan Tajikistan (, ; tg, Тоҷикистон, Tojikiston; russian: Таджикистан, Tadzhikistan), officially the Republic of Tajikistan ( tg, Ҷумҳурии Тоҷикистон, Jumhurii Tojikiston), is a landlocked country in Centr ...

and

Uzbekistan Uzbekistan (, ; uz, Ozbekiston, italic=yes / , ; russian: Узбекистан), officially the Republic of Uzbekistan ( uz, Ozbekiston Respublikasi, italic=yes / ; russian: Республика Узбекистан), is a doubly landlocked co ...

. The Late Triassic layers rest on top of

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

basement A basement or cellar is one or more Storey, floors of a building that are completely or partly below the storey, ground floor. It generally is used as a utility space for a building, where such items as the Furnace (house heating), furnace, ...

with local Permo-Triassic

molasse __NOTOC__ The term "molasse" () refers to sandstones, shales and conglomerates that form as terrestrial or shallow marine deposits in front of rising mountain chains. The molasse deposits accumulate in a foreland basin, especially on top of flys ...

sediments. The section consists of mudstones,

s, conglomerates and fanglomerates. This wide variety of siliciclastic rocks reflects the complex spatial and temporal pattern of depositional sub-environments including

alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but a ...

s, sandflats, swamps, back-swamp areas, and littoral to profundal lake zones. The fluvio-lacustrine deposits of the Madygen Formation belong to one of only a few occurrences of continental Triassic beds in Central Asia.Fischer et al., 2007, p.42 The formation was deposited during the

Carnian Pluvial Event The Carnian pluvial episode (CPE), often called the Carnian pluvial event, was an interval of major change in global climate synchronous with significant changes in Earth's biota both in the sea and on land. It occurred during the latter part of ...

(CPE), a global humid event leading to high extinction levels of various groups globally. The CPE led to anoxic conditions, most notably in the

South China Block The Yangtze Plate, also called the South China Block or the South China Subplate, comprises the bulk of southern China. It is separated on the east from the Okinawa Plate by a rift that forms the Okinawa Trough which is a back-arc basin, on the ...

. The area where the Madygen Formation was deposited formed part of the Cimmerian microcontinent, a slab of crust that collided with

Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pan ...

during the Cimmerian orogeny in later Mesozoic times. This orogeny led to the disappearance of the

Paleo-Tethys Ocean The Paleo-Tethys or Palaeo-Tethys Ocean was an ocean located along the northern margin of the paleocontinent Gondwana that started to open during the Middle Cambrian, grew throughout the Paleozoic, and finally closed during the Late Triassic; ex ...

Petroleum geology

The formation grades from bottom to top from alluvial to fluvial into a thick succession of lacustrine mudstones, followed by an alluvial package, on top of which lacustrine, fluvial, deltaic and alluvial layers were deposited.Berner et al., 2009, p.2 The hydrocarbon potential of samples of the Madygen Formation ranges from poor to excellent. The sediments containing more than 0.5%

Total Organic Carbon Total organic carbon (TOC) is the amount of carbon found in an organic compound and is often used as a non-specific indicator of water quality or cleanliness of pharmaceutical manufacturing equipment. TOC may also refer to the amount of organic c ...

(TOC) may be regarded as sources of gaseous hydrocarbons rather than of oil.Berner et al., 2009, p.5 The Hydrogen Index (HI) of outcrop samples reaches 100 and the maximum recorded maturity (Ro) is 0.8.Berner et al., 2009, p.6

Paleontological significance

During the 1960s, Russian paleontologists recovered an unusually rich fossil content in the type strata of the Madygen Formation, including abundant macrophytes, more than 20,000 insect remainsKelly, 2018, p.62 and unique small reptiles with well preserved soft tissue. '' Spirorbis''-like polychaete worm tubes, crustaceans (

ostracod Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typic ...

s, kazacharthrans, malacostraca), freshwater

pelecypod Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, biva ...

s and gastropods are known from shallow to deeper lake environments. Non-aquatic insects are among the most common fossil remains of the Madygen Formation. These include representatives of the orders Ephemeroptera,

Odonata Odonata is an order of flying insects that includes the dragonflies and damselflies. Members of the group first appeared during the Triassic, though members of their total group, Odonatoptera, first appeared in Late Carboniferous. The two co ...

Notoptera The wingless insect order Notoptera, a group first proposed in 1915, had been largely unrecognized since its original conception, until resurrected in 2004. As now defined, the order comprises five families, three of them known only from fossils ...

Blattodea Blattodea is an order of insects that contains cockroaches and termites. Formerly, termites were considered a separate order, Isoptera, but genetic and molecular evidence suggests they evolved from within the cockroach lineage, cladistically m ...

Titanoptera Titanoptera is an extinct order of neopteran insects from late Carboniferous to Triassic periods. Titanopterans were very large in comparison with modern insects, some having wingspans of up to or even . Description Titanopterans are relate ...

Ensifera Ensifera is a suborder of insects that includes the various types of crickets and their allies including: true crickets, camel crickets, bush crickets or katydids, grigs, weta and Cooloola monsters. This and the suborder Caelifera (grasshop ...

Caelifera The Caelifera are a suborder of orthopteran insects. They include the grasshoppers and grasshopper-like insects, as well as other superfamilies classified with them: the ground-hoppers ( Tetrigoidea) and pygmy mole crickets ( Tridactyloidea). ...

Rhynchota Hemiptera (; ) is an order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, assassin bugs, bed bugs, and shield bugs. They range in size from to a ...

Auchenorrhyncha The Auchenorrhyncha suborder of the Hemiptera contains most of the familiar members of what was called the "Homoptera" – groups such as cicadas, leafhoppers, treehoppers, planthoppers, and spittlebugs. The aphids and scale insects are the ot ...

, Stenorrhyncha,

Coleoptera Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

, Hymenoptera,

Trichoptera The caddisflies, or order Trichoptera, are a group of insects with aquatic larvae and terrestrial adults. There are approximately 14,500 described species, most of which can be divided into the suborders Integripalpia and Annulipalpia on the ...

and Diptera. Traces of insect larvae are preserved in near-shore lake deposits. Fish remains mostly represent endemic genera assigned to the actinopterygian families Evenkiidae ('' Oshia''),

Palaeoniscidae Palaeoniscidae is an extinct family of ray-finned fishes (Actinopterygii) ascribed to the order Palaeonisciformes. The family includes the genus ''Palaeoniscum'' and potentially other Palaeozoic and Mesozoic early actinopterygian genera. The ...

('' Ferganiscus'', '' Sixtelia'') and '' Megaperleidus'' and ''

Alvinia ''Alvania'' is a genus of minute sea snails, marine gastropod mollusks or micromollusks in the family Rissoidae. ''Alvania'' as currently used may not be monophyletic. Distribution These marine species can be found worldwide (except in the An ...

''. The actinopterygian ''

Saurichthys ''Saurichthys'' (from el, σαῦρος , 'lizard' and el, ἰχθῦς 'fish') is an extinct genus of predatory ray-finned fish from the Triassic period. It type genus family Saurichthyidae ( Changhsingian-Middle Jurassic), and the larges ...

'' and the dipnoan '' Asiatoceratodus'' are cosmopolitan taxa also recorded in the Madygen Formation. Two distinctive elasmobranch egg capsule types, i.e. ''

Palaeoxyris ''Palaeoxyris'' is a morphogenus of eggs cases, widely thought to have been produced by hybodonts, with a predominant occurrence in ancient freshwater environments. They comprise a beak, a body and a pedicle. They display a conspicuous right-ha ...

'', indicating a small ''

Lissodus ''Lissodus'' is an extinct genus of freshwater shark. It lived from the Early Carboniferous stage 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 ...

''- or '' Lonchidion''-like hybodont shark and an indeterminate capsule type, imply the presence of two different elasmobranch species which used the freshwater environments of the Madygen Formation as spawning grounds. Tetrapods are known from a probably larval urodelan (''

Triassurus ''Triassurus'' is an extinct genus of amphibian, and the oldest member of Caudata (salamanders and close relalatives). It is known from the Middle to Upper Triassic (Ladinian-Carnian) aged Madygen Formation in Kyrgyzstan. The type species is ' ...

''), a small procynosuchid cynodont ('' Madysaurus''), a gliding reptile (''

'') and the enigmatic diapsid '' Longisquama''.Voigt et al., 2007, p.162

Fossil content

Amphibians

Reptiles

Synapsids

Cartilaginous fishes

Fishes

The following fish fossils were found in the formation:Kogan et al., 2009, p.142Franeck et al., 2013, p.54

Arthropods

Flora

Insect fauna correlations

Progonocimicidae The Progonocimicidae are an extinct family of true bugs in the suborder Coleorrhyncha. Progonocimicidae fossils have been found in Europe, Asia, Australia, and South America. Families preserved in the fossil record of Coleorrhyncha include the e ...

found in the formation are also recorded in the Carnian

Los Rastros Formation The Los Rastros Formation is a Ladinian to Carnian fossiliferous formation of the Agua de la Peña Group in the Ischigualasto-Villa Unión Basin in northwestern Argentina. Fossil theropod tracks,Weishampel et al., 2004, pp. 517-607 as well as many ...

of Argentina, the Norian Blackstone and

Mount Crosby Formation Mount is often used as part of the name of specific mountains, e.g. Mount Everest. Mount or Mounts may also refer to: Places * Mount, Cornwall, a village in Warleggan parish, England * Mount, Perranzabuloe, a hamlet in Perranzabuloe parish ...

s of Australia, and the Norian to Rhaetian Tologoi Formation of Kazakhstan.Kelly, 2018, p.190 Permochoristidae are also known from the Carnian Potrerillos and

Cacheuta Formation The Cacheuta Spa ( es, Termas de Cacheuta, ) is a bathing establishment in Argentina exploiting the natural hot springs at Cacheuta on the Mendoza River in the foothills of the Andes.Huangshanjie Formation of China, the Norian Blackstone and Mount Crosby Formations of Australia; the Norian to Rhaetian Tologoi Formation of Kazakhstan, the Sinemurian

Dzhil Formation Dzhil may refer to: * Jil, Armenia * Cil, Azerbaijan Cil (also, Kazımlı Cil and Dzhil’) is a village and municipality in the Lankaran Rayon of Azerbaijan. It had a population of 2,279 as of 2007. Notable natives * Allahshukur Pashazadeh, ...

of Kyrgyzstan and the Toarcian

Posidonia Shale The Posidonia Shale (german: Posidonienschiefer, also called Schistes Bitumineux in Luxembourg) geologically known as the Sachrang Formation, is an Early Jurassic (Toarcian) geological formation of southwestern and northeast Germany, northern Swi ...

of Germany.Kelly, 2018, p.186 '' Orthophlebia'' had a relatively broad distribution in the Late Triassic as it is also found in the Sinemurian Badaowan Formation of China and Dzhil Formation of Kyrgyzstan, the Pliensbachian

Makarova Formation Makarov/Makarova (masculine/feminine) (russian: Макаров/Макарова) is a Russian surname that is derived from the male given name Makar (in turn derived from the Greek name Macarius) and literally means ''Makar's''. It is the 29th mo ...

of Russia and Sulyukta Formation of Tajikistan; the Toarcian

Whitby Mudstone Formation The Whitby Mudstone is a Toarcian (Early Jurassic; ''Falciferum''-''Bifrons'' in regional chronostratigraphy) geological formation in Yorkshire and Worcestershire, England.Cheremkhovo Formation Cheremkhovo ( rus, Черемхо́во, p=tɕɪrʲɪmˈxovə) is a town in Irkutsk Oblast, Russia, located on the Trans-Siberian Railway. History Cheremkhovo was founded in 1772. Administrative and municipal status Within the framework of adm ...

of Russia, and the Early Jurassic

Kushmurun Formation Kushmurun ( kk, Құсмұрын; russian: Кушмурун) is a brackish lake in the Kostanay Region, Kazakhstan. Kushmurun is one of largest natural waterbodies of Kazakhstan. It lies in the northern sector of the Turgay Basin, at the border be ...

of Kazakhstan.Kelly, 2018, p.185

Haglidae The family Prophalangopsidae are insects belonging to the order Orthoptera. They are the only extant members of the superfamily Hagloidea. There is only one extant genus in North America, where they are known as grigs, four genera in Asia, and ...

were also recorded in the Koldzat and Tologoi Formations of Kazakhstan, in the Carnian Cacheutá Formation of Argentina, the Carnian to Norian

Molteno Formation The Molteno Formation is a geological formation found in several localities in Lesotho and South Africa. It lies mainly south of Maseru, near Burgersdorp, Aliwal North, Dordrecht, Molteno, and Elliot. It extends as far north as Matatiele in the ...

of South Africa and Lesotho, and the Norian Mount Crosby Formation of Australia.Kelly, 2018, p.182

References

Bibliography

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * {{cite LSA , last=Becker-Migdisova , first=E.E , year=1953 , title=Dva predstavitelya poluzhestkokrylykh nasekomykh iz urochishcha Madygen , journal=Doklady Akademii Nauk SSSR , volume=90 , pages=461–464 Geologic formations of Kyrgyzstan Geologic formations of Tajikistan Geologic formations of Uzbekistan Conglomerate formations Mudstone formations Sandstone formations Alluvial deposits Deltaic deposits Fluvial deposits Lacustrine deposits Fossiliferous stratigraphic units of Asia Paleontology in Kyrgyzstan Formations Formations