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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Archalyk Formation

Archalyk Fm

Period:

Ordovician

Age Interval:

Upper Ordovician (O_2-3), C1

Province:
Central W Tajik

Type Locality and Naming

In the Zeravshan-Gissar district, A.I. Lavrushevich considers it possible to distinguish two types of sections for sediments of this age: the Shahriomon and Zahonin types, which are connected by sections of intermediate character.

Synonym: Archalyk suite, Aрчалыкской: свиты, Archalik suite

Reference section:

Lithology and Thickness

In Tajikistan, in the basin of the Saromat River, the Archalyk Fm has a thickness of about 200 m and is composed of thinly bedded organogenic limestones, dolomites, and, to a lesser extent, quartz sandstones.

Lithology Pattern:

Dolomitic limestone

Relationships and Distribution

Lower contact

Conformably underlain by Shahriomon Fm

Upper contact

Overlain by the Lower Silurian deposits.

Regional extent

In the Zeravshan-Gissar district, in the area of the Shahriomon Pass (type section)

GeoJSON

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Fossils

with Streptelasma saelaboni Scheffen, Brachyelasma duncani (Dyb.), Gissarophyllum paligerum Lavrus., Holorrhynchus giganteus Kiaer, and other fossils of the Ashgillian stage.

Age

There are two viewpoints regarding the age of the upper part of the Archalyk Fm (upper Archalyk beds). A. I. Lavrusevich (1972) considers that the upper Archalyk beds belong to the Upper Ordovician. Other researchers (Mufthiev et al., 1971; Decision..., 1969) refer them to the lower parts of the Llandovery. Here, it is presented in Upper Ordovician for schematic stratigraphic representation purpose.

Age Span:

Beginning stage:

Katian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

452.75

Ending stage:

Hirnantian

Fraction up in the ending stage:

1.0

Ending date (Ma):

443.07

Depositional setting

Depositional pattern:

Additional Information

Compiler:

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