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

Yagnob Formation

Yagnob Fm

Period:

Ordovician, Cambrian

Age Interval:

Drumian-Dapingian, Z1

Province:
Zarafshan-N.Gissar

Type Locality and Naming

Along the Yagnob River, Zarafshan Range. A.P. Markovsky, 1934 (287, pp.1-49). Stratotype in the valley of the Anzob River, Gissar Range.

Synonym: Yagnob Suite, Ягнобская св.

Lithology and Thickness

Lower part - gneiss-like rocks with layers of quartzites and amphibolites; Middle - muscovite-chlorite-quartz, albite-chlorite-epidote-actinolite, quartz-schistose; Upper - phyllites, schistose and quartzitic sandstones, gravellites. Small bodies of marbles are encountered. Thickness more than 1000 m.

Lithology Pattern:

Gneiss

Relationships and Distribution

Lower contact

Contacts are tectonic.

Upper contact

Contacts are tectonic.

Regional extent

South slope of the Zarafshan Range.

GeoJSON

null

Fossils

In the lower part of the suite, Cambrian spores (143). In the upper part, remains of late Ordovician (Ashgill) rugosans *Grevingkia conteta* Neuman. (261).

Age

The age of the Yagnob Fm remains controversial. Some researchers consider it Precambrian (101; 256), others - Vendian?-lower Paleozoic (379) or lower Paleozoic (E.A. Portnyagin, V.I. Popov, D.P. Rezvoy, N.G. Vlasov, etc.). V.R. Martyshev (289) refers it to metamorphosed analogs of middle Devonian formations. M.A. Akhmedjanov et al. (73), due to the insufficiency of materials on stratigraphy, lithology, metamorphism, and age relationships, recommend referring the suite to undifferentiated Precambrian-lower Paleozoic formations. On the State Geologic Map-500 of Uzbekistan (460), it is assigned a Cambrian-middle Ordovician age based on finds of Cambro-Ordovician fossils.

Age Span:

Beginning stage:

Drumian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

504.50

Ending stage:

Dapingian

Fraction up in the ending stage:

1.0

Ending date (Ma):

469.42

Depositional setting

Depositional pattern:

Additional Information

Compiler:

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