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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Lower Vanch Outcrops Formation

Lower Vanch Outcrops Fm

Period:

Silurian

Age Interval:

Llandovery-Wenlock (S₁), V1

Province:
SE Tajik (Central W Pamir)

Type Locality and Naming

Synonym: outcrops of the Lower Silurian

Reference section:

Lithology and Thickness

In the basin of the River Kozindy, the Lower Silurian is composed at the bottom of dark and gray organogenic carbonates with subordinate interlayers of sandstones and siltstones up to 200 m thick (according to V. I. Dronov - 320 m), at the top by brown quarzitic sandstones, passing higher into sandy dolomites with a total thickness of about 150 m.

The upper part of the Lower Silurian section, originally, possibly, built upon the above-described (according to V. I. Dronov - a different type of section), is known in all zones of the scaly structure and is represented at the bottom by greenish, strongly altered diabase porphyrites and quartz sandstones, in the middle part - by gray and purple limestones, and at the top - by green and raspberry slates. The total thickness is 150-270m.

Lithology Pattern:

Sandy limestone

Relationships and Distribution

Lower contact

in some cases (River Kozindy), lies conformably on the slates of the Kozyndyn Fm of the Ordovician (Dronov, 1955), in others (rivers Kukurtjilga, Saridjilga, Akbaytal, etc.) The relationships between these two parts of the section are everywhere tectonic.

Upper contact

conformably overlies the limestones of the Upper Silurian (Karapetov, 1960). The relationships between these two parts of the section are everywhere tectonic.

Regional extent

In the Muzkol range, the outcrops of the Lower Silurian are confined to the zones of development of the Akbaytal, South Rangkul, and North Ak-Su tectonic scales.

GeoJSON

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Fossils

In the limestones, there are remnants of tabulate corals Favosites gothlandicus Lam., Catenipora ex gr. sindoensis (Ozaki), Heliolites cf. interstinctus Lin., etc., the complex of which is most typical for the late Llandovery - early Wenlock (Lelius, 1963), as well as Lower Silurian brachiopods Pentamerus oblongus Sow., Parmorthis neocrassa Nikif., etc.

Age

The fossil data indicates late Llandovery - early Wenlock. Due to their conformable bedding under Ludlovian layers and the stems of crinoids enclosed in the limestones, the described deposits are conditionally attributed to the upper Wenlock (Qarapetov, 1960) for the the upper part of the Lower Silurian section.

Age Span:

Beginning stage:

Telychian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

438.59

Ending stage:

Sheinwoodian

Fraction up in the ending stage:

1.0

Ending date (Ma):

430.62

Depositional setting

Depositional pattern:

Additional Information

Compiler:

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