Neogene

Paleogene

Cretaceous

Jurassic

Triassic

Permian

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

Neoproterozoic

Mesoproterozoic

Paleoproterozoic

Main source = Abduazimova, Z.M. (Ed.), 2001. Stratigraphic Dictionary of Uzbekistan. IMR (Institute of Mineral Resources), Tashkent, 580 pp. (In Russian) Translated to English by the GeoGPT group, Zhejiang Lab, Hangzhou, China--see About

Nakrut Formation

Nakrut Fm

Period:

Silurian

Age Interval:

lower-middle Llandovery, N7

Province:
Nuratau

Type Locality and Naming

Along the Say Nakrut, N. Nuratau. N.R. Asatullaev in 1970 (1972), detailed study by R.R. Usmanov et al. (1989f.), R.S. Khan et al. (1989f.), Z.M. Abduazimova et al. (1989f.). Stratotype Along Nakrutsay.

Synonym: Nakrutskaya Suite, Накрутская св.

Lithology and Thickness

Upper part (thickness 20-80m) - carbonaceous-siliceous-micaceous slates with layers of argillites, essentially quartz greenish-gray and fine-grained silty-claystone (aleuropelites). In the uppermost parts are coarse-grained polymictic varieties of sandstones.

Lower part of the suite (thickness 15-25m) - black carbonaceous-siliceous-micaceous, carbonaceous-quartz-micaceous thin-plate slates with lenses (0.5-1 cm) of dark siliceous-phosphatic rock.

The total thickness of the suite is 30-105m (11; Abdazimova, 1996; 165).

Lithology Pattern:

Sandy_claystone

Relationships and Distribution

Lower contact

The lower contact with the Badamchalin Fm is tectonic

Upper contact

The upper one is conformable with the Dzhazbulak Fm. R.R. Usmanov et al. (1989), V.S. Korsakov et al. (1993) consider the contacts with the Badamchalin Fm and Dzhazbulak Fm to be conformable.

Regional extent

The southern slope of the North Nuratau range extends from the Pangat gorge in the west to the Sanzar River in the southeast; the range of Y. Nuratau - from Sharlaksaia in the west to Karakchatay, including the east; the Gobduntay Mountains. I.A. Pyanovskaya et al. (371) in the Y. Nuratau included the Nakrut Fm in the composition of the Sartbulak.

GeoJSON

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Fossils

Upper part – Graptolites in the span of zones Demirastrites convolutus–Spirograptus turriculatus, covering the interval of the upper middle part of the Llandovery - Cephalograptus tubulariformis (Nich.), Petalograptus folium (His.), P. folium tornquisti(Bouček. et Přibyl.); chitinozoa - Eisenackitina dolioliformis Umn., E. oviformis (Eis.), Conochitina edjelensis Taug.

Lower part – Graptolites in the span of zones Akidograptus ascensus–Demirastrites triangulatus, corresponding to the Lower-Middle Llandovery - Climacograptus miserabilis Elles. et Wood., Akidograptus ascencus Davis., Dimorphograptus sp., Cystograptus vesiculosus (Nich.), Limpidograptus posohovae Chal., Demirastrites triangulatus (Harkh.), Coronograptus gregarius (Lapw.) and others.

Age

On the State Geological Map-500 of Uzbekistan (460) the suite is assigned an early Silurian age.

Age Span:

Beginning stage:

Rhuddanian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

441.78

Ending stage:

Aeronian

Fraction up in the ending stage:

1.0

Ending date (Ma):

438.59

Depositional setting

Depositional pattern:

Additional Information

Compiler:

Z.M.Abdazimova – In: GeoGPT translation of: “Abduazimova, Z.M. (Ed.), 2001. Stratigraphic Dictionary of Uzbekistan. IMR (Institute of Mineral Resources), Tashkent, 580 pp. (In Russian)”