Kamyshbashin Formation

Kamyshbashin Fm

Period:

Triassic

Age Interval:

Upper Triassic (Rhaetian- Sinemurian), F9a

Province:
Fergana

Type Locality and Naming

Along the Kamyshbash River (Shorsu), South Fergana. V.V. Vseber, 1934 (135, p. 209). Stratotype Along the Kamyshbashy (Shorsu) section, South Fergana.

Synonym: Kamyshbashinskaya Formation, Камышбашинская св.

Lithology and Thickness

A.T. Burakova, V.V. Kurbatov, I.Yu. Neustrueva, et al. (121) subdivided the suite into the Lower Kamyshbashy (Upper Triassic) and Upper Kamyshbashy (Lower Jurassic) sub-suites. The Lower Kamyshbashy sub-suite is characterized by cyclic alternation of variegated clays, siltstone (aleurolites), lenticular layers of conglomerates, gravels, and polymictic sandstones. Thickness up to 224 m. The Upper Kamyshbashy sub-suite - variegated clays, siltstone (aleurolites), sandstones of lacustrine-floodplain facies. Thickness 300-370 m.

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

The Lower Kamyshbashy sub-suite transgressively overlies the Paleozoic, Madygen Fm

Upper contact

The Lower Kamyshbashy sub-suite is conformable or with traces of erosion overlain by the Upper Kamyshbashy sub-suite. Upper Kamyshbashy sub-suite transgressively overlain by the Sogul Fm.

Regional extent

The foothills of the Turkestan Range in South Fergana (Kamyshbashy, Madygen, Shurab). Facies and age analogs are the Sandzhar Fm and Changis Fm

GeoJSON

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Fossils

The Lower Kamyshbashy sub-suite contains layers with large plant remains - Schizoneura dondwanensis and Lepidopteris elegans: Danaeopsis marantaceae (Schimper) Halle, Diplazites dentatus Sixt., Lepidopteris elegans (Brick), etc. (120); freshwater ostracods Daswinula cf. major Tones, D. aff. globosa Duff., etc.; conchostracans - Eulimnadia kustanaica Novojil., Pseudestheria sp., Glyptousmussia sp., Estheriina kawasakii Ozawa et Watan., Lioestheria hiboi Kob., etc.

The Upper Kamyshbashy sub-suite contains large plant remains - Equisetites ex gr. beanii (Bunb.) and others, freshwater ostracods - Darvinula isfarensis Neustr., D. aff. globosa Duff., Ifarella elongata Neustr., etc.; freshwater bivalve mollusks - Unio schaborovi Tschern., Sibireconcha chodzhakelenica Martins. et Mikulin, etc.

Age

Freshwater ostracods and large plant remains confirm the Late Triassic (Rhaetian) age of the Lower Kamyshbashy sub-suite. Organic remains do not contradict the assignment of the Upper Kamyshbashy sub-suite to the Early Jurassic. A. (135) distinguished the Kamyshbashy suite of the Late Triassic; M.I. Brick (120) named the suite of the mountains and distinguished the Triassic lower variegated suite and the Rhaetian-Early Liassic middle slate suite, while T.A. Sixtel (407; 408) divided the Kamyshbashin Fminto the lower sub-suite of the Late Triassic and the upper sub-suite, which she dated to the Early Jurassic - lower Bajocian. At the Tashkent Conference (382, Table 12), the Kamyshbashin Fmwas dated to the Late Triassic, and the overlying Upper Kamyshbashy sub-suite (Along T.A. Sixtel) was renamed the Sulyukta Fm, which was dated to the Early Jurassic - lower Bajocian. V.V. Kurbatov, V.I. Troitsky (165; 415; 422) distinguish two sub-suites of Late Triassic and Early Jurassic age.

Age Span:

Beginning stage:

Rhaetian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

205.74

Ending stage:

Sinemurian

Fraction up in the ending stage:

1.0

Ending date (Ma):

192.90

Depositional setting

Depositional pattern:

Additional Information

Compiler:

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