Neogene

Paleogene

Cretaceous

Jurassic

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Carboniferous

Devonian

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Mesoproterozoic

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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

Akbasay Formation

Akbasay Fm

Period:

Devonian

Age Interval:

Lower-Middle Devonian, Z1a

Province:
Zarafshan-N.Gissar

Type Locality and Naming

Named after the Akbasa stream, Zeravshan Ridge. A.I. Lavrushevich, V.I. Lavrushevich, V.D. Saltovskaya, 1973 (263, p. 19-20).

Synonym: Akbasai Suite, Акбасайская св., Akbasa Fm, Akbassay Fm

Lithology and Thickness

Lower part consists of platy and thin-bedded jasper-like cherts with layers of siliceous-clayey shales, tentaculitid, crinoidal-detrital, and fragmental limestones, and limestone breccias. Upper part - variegated (red, raspberry, green, gray, purple) clayey, clayey-siliceous siltstone (aleurolites), shales with rare layers of clayey limestones, gravellites, tuffs, sandstones. Thickness: 180-600m.

Lithology Pattern:

Siltstone

Relationships and Distribution

Lower contact

The lower boundary is normal with the Arg Gr and has a sliding character over time, starting from the Lochkovian level and ending in the upper Devonian (165).

According to E.G. Fedorov et al. (1987), in some places, it lies on the limestones of the Kashkadarya Fm reef complex. Stratified formations of Tajikistan (379) - lower-middle Devonian. Thickness 400-500m, lies conformably on the Arg Gr

Upper contact

According to E.G. Fedorov et al. (1987), it is overlain by the Shakhsay Fm. Stratified formations of Tajikistan (379) is overlain with stratigraphic unconformity by the Marguzor Fm of Tournaisian?-early Visean age; 3.3.

Regional extent

Zeravshan-Gissar mountain region. Akbasay Fm and the overlying Marguzor Fm are considered subsuite of the Pushtnavat Fm; in the Strat. sl. (441) - lower-middle Devonian, corresponds to the lower sub-suite of the Pushtnavat Fm. Thickness 400-450m.

GeoJSON

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Fossils

Contains tentaculitids - Paranowakia obuti Bouček, P. aff. intermedia Barr., Nowakia ex gr. acuaria (Richter); conodonts - Pandorinellina cf. optima (Mosk.), P. steinhornensis miae (Bult.), Pelekysgnathus cf. serratus Carls et Gandl, Polygnathus cf. dehiscens Philip et Jackson et al.; tabulates - Favosites eifeliensis Nich., F. placenta Rom., Pachyfavosites kozlowskii Sok., rugosans - Xystriphyllum sibiricum Bulv.; stromatoporoids - Amphipora ramosa Phil.; brachiopods - Conchidiella sp. and others, characterizing the age of the Akbasay Fm within the entire Devonian system.

Biostratigraphically, within the Akbasay Fm, all subdivisions of the general and regional scales are recognized and distinguished based on the zonal conodont sequence.

Age

The age and span of the Fm are understood differently. V.R. Martyshev (289) - middle Devonian (living) - lower Tournaisian.Mufitiev, V.B. Aver'yanov et al. (1978) in the explanatory note to the working legend of the Zarafshan-Gissar series of sheets considered that the remains of fauna from various horizons of the Silurian and Devonian are re-deposited, and the age of the Akbasay Fm should be determined as lower-middle Carboniferous (460).

Age Span:

Beginning stage:

Givetian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

385.30

Ending stage:

Frasnian

Fraction up in the ending stage:

1.0

Ending date (Ma):

371.10

Depositional setting

Depositional pattern:

Additional Information

Compiler:

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