Tonashin Formation

Tonashin Fm

Period:

Jurassic

Age Interval:

Aalenian, U4

Province:
Ustyurt-Sultanuzdag

Type Locality and Naming

Along the Tona Mountain, Mangyshlak Peninsula. T.A. Ishina, 1961 (476, p.219). Tonashin Fm is exposed by wells in South Mangyshlak, South Turkmenistan, and analogs on Ustyurt. Stratotype on Tona Mountain (446). In South Ustyurt, it was distinguished (383, table 4, sheet 2) as the Lower Tona subsuite (see Takhtakair Fm) and undivided Upper Tona subsuite and Karadiirmen Fm (see Berdak Fm).

Synonym: Tonashinskaya Suite, Тонганинская св.

Lithology and Thickness

Divided into two subsuites (91; 383, table 4, sheet 2).

Upper Tona subsuite - alternation of sandy and silty (aleurolitic) clayey rocks with coal seams. Thickness 40m.

Lower Tona subsuite - cross-bedded polymictic sandstones with lenses of conglomerates. Thickness up to 230m.

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

Upper Tona subsuite - Along the stratigraphy, it lies on the Lower Tona subsuite

Lower Tona subsuite - Lies with erosion on the Paleozoic or Kokalin Fm

Upper contact

Upper Tona subsuite – is transgressively overlain by the Karadiirmen Fm

Lower Tona subsuite – overlain with erosion by the Upper Tona subsuite.

Regional extent

Eastern part of the Mangyshlak Peninsula, in the Tona uplift area, Kelendy area near the Kugusem village

GeoJSON

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Fossils

Upper Tona subsuite – Contains freshwater bivalve mollusks - Subcardinia sibirensis Mart., Pseudocardinia lacustris Kol. and others; large plant remains Coniopteris angustiloba Brick, Phlebopteris polypodioides Brongn. and others.

Lower Tona subsuite – Contains spore and pollen assemblages (see Takhtakair Fm).

Age

Middle Jurassic (Aalenian)

Age Span:

Beginning stage:

Aalenian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

174.70

Ending stage:

Aalenian

Fraction up in the ending stage:

0.65

Ending date (Ma):

172.23

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)”