Cenozoic

Cretaceous

Jurassic

Triassic

Permian

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

Neoproterozoic

Main source = Baratov, R.B., et al. (1976). Subdivisions of stratified and intrusive rocks of Tajikistan. Publishing House "Donish", Dushanbe, 269 pp. plus tables. Provided by Dr. Jovid Aminov, Nazarbayev University, Astana, Kazakhstan Translated to English by the GeoGPT group, Zhejiang Lab, Hangzhou, China--see About

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Vashan Formation

Vashan Fm

Period:

Carboniferous

Age Interval:

Lower-Middle Carboniferous (C₁ vs), S2

Province:
North Tajik

Type Locality and Naming

It was distinguished by V.R. Martyshev (1958).

Synonym: Vashanskaya suite

Reference section:

Lithology and Thickness

Claystone in lower half, limestone in upper half. The lower half is composed of siliceous shales, dark gray, black, and green in color, containing interlayers of argillaceous limestones and jasper. The upper half of the suite is formed by characteristic thin-bedded argillaceous limestones, black in fracture and yellow-brown on the surface. They contain interlayers of polymict greenish-gray sandstones, gray siliceous shales, and gravels. The thickness of the Vashan Fm (вашанской свиты) is 500-1000 m.

Lithology Pattern:

Clayey limestone

Relationships and Distribution

Lower contact

It lies transgressively, without noticeable angular unconformity, on the slates of the Wenlock-Ludlow Garibak Fm, гарибакской свиты

Upper contact

It is covered with analogous contacts by the phyllite of the Upper Moscow-Upper Carboniferous Obizard Fm.

Regional extent

It is widespread in the Turkestan region in the valley of the Zeravshan River.

GeoJSON

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Fossils

According to V.D. Saltykovskaya (1964), in the lower half of the Vashan Fm (вашанской Свиты), there are remains of Lower Namurian Goniatites Cravenoceras cowlingense Bisat., Cr. arcticum Libr., Cr. alaicum Libr., Dimorphoceras cf. plicatilis Noore, D. ex gr. looney (Phill.), and throughout the section - remains of Lower Carboniferous foraminifera.

Age

Based on these data, the age of the Vashan Fm (вашанской свиты) is estimated conditionally as Namurian. It is quite likely that the lower part of the suite belongs to the the Viséan, while the upper ones to the Middle Carboniferous, as was suggested by V. R. Martyshov (1958) and V. D. Saltovskaya (1964). A. S. Shadchinev (1970) included the limestones with goniatite remains in the Middle Viséan - Lower Moscovian deposits. He conditionally referred the remaining part of the deposits (under the name of the Demnorinskaya Suite (демноринской Свиты) to the upper sub-stage of the Moscovian stage, assuming that the remains of the Lower Carboniferous foraminifera are found here in a redeposited state. It is hard to agree with this, as among the goniatite-bearing limestones, Namurian layers contain interbeds of the same siliceous shales as in the rest of the Vashan Fm (вашанская свита), emphasizing its unity. It should be emphasized that the Vashan Fm (вашанская свита) is insufficiently studied.

Age Span:

Beginning stage:

Visean

Fraction up in beginning stage:

0.0

Beginning date (Ma):

346.73

Ending stage:

Moscovian

Fraction up in the ending stage:

0.5

Ending date (Ma):

311.09

Depositional setting

Depositional pattern:

Additional Information

Compiler:

Extracted from Baratov, R. B. (1976). Subdivisions of stratified and intrusive rocks of Tajikistan. Donish, Dushanbe, 276.