Gaz Formation

Gaz Fm

Period:

Carboniferous

Age Interval:

Lower–Middle Carboniferous (Serpukhovian–Bashkirian), F10b

Province:
Fergana

Type Locality and Naming

Along the Gaz, South Fergana. V.N. Weber in 1909 (166, p. 274), but also known under the name "Gaz" beds (321). Stratotype in the interfluve of the Aksu-Karabulak. Lower formation in the Andygen Gr.

Synonym: Gaz Suite, Gaz beds, Газская св.

Lithology and Thickness

Bedded limestones, often clastic-organogenic with layers and lenses of cherts. Thickness up to 450 m.

Lithology Pattern:

Limestone

Relationships and Distribution

Lower contact

Along the bedding, it lies on the Peshkaut Fm

Upper contact

It is often overlain with erosion or conformably by the Kauzan Fm

Regional extent

South Fergana, northern foothills of the Alai Range. The most complete sections are in Kyrgyzstan, locally in Uzbekistan. It is part of the Andygen Gr.

GeoJSON

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Fossils

In the lower part, Serpukhovian foraminifers - Eostaffelina profvae (Raus.), Asteroarchaediscus micus Pojark.; brachiopods - Productus concinnus Sow., Marginifera schartimiensis (Jan.); Goniatites - Cravenoceras sp.; in the upper part, Bashkirian foraminifers - Pseudostaffella antiqua (Dutk.), Neoarchaediscus ex gr. gregorii (Dain.); brachiopods - Choristites bisulcatiformis Semich. In the very upper horizons - foraminifers first Profusulinella parva Lee et Chen, P. cf. primitiva Sosn.

Age

It belongs to the Serpukhovian-Bashkirian stage of the Lower-Middle Carboniferous (165; 439). Some researchers include deposits containing Early Moscovian foraminifers in the suite (460).

Age Span:

Beginning stage:

Serpukhovian

Fraction up in beginning stage:

0.1

Beginning date (Ma):

329.65

Ending stage:

Bashkirian

Fraction up in the ending stage:

0.7

Ending date (Ma):

317.63

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)"