Oydynbulak Formation

Oydynbulak Fm

Period:

Ordovician

Age Interval:

Ashgillian, K9a

Province:
Kyzylkum Region

Type Locality and Naming

At the Oydybulak gorge, Kuldjuktau Mountains, Central Kyzylkum. Ya.B.Aysanov, 1968 (43, p.62), 1978 (44, p.15).

Synonym:

Lithology and Thickness

According to A., at the base of the section - nodular organogenic limestones of dark gray and black color with lenses and thin layers of bluish and dark green slates, Thickness: 6m; they are overlain by dark gray flaggy detrital limestones with inclusions of dark siliceous rocks in large quantities, Thickness: 30m; Middle part - thin-bedded limestones with siliceous streaks, Thickness: 35m, Upper part consists of clayey flaggy, thin-bedded dolomites of light brown color, Thickness: 35m. Total thickness of the suite: 106m.

Lithology Pattern:

Dolomite

Relationships and Distribution

Lower contact

According to A., the Oydynbulak Fm conformably overlies the Kazakasuy Fm

Upper contact

According to A., the Oydynbulak Fm it is also conformably overlain by the Yangikazgan Fm (44; 122; 165; 460).

Regional extent

Central Kyzylkum, northern slope, eastern and western parts of the Kuldjuktau Mountains, upper reaches of the Oydybulak gorge, southern and southeastern parts of the Bashguzhumdy col, northern part of the Yangikazgan col.

GeoJSON

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Fossils

Corals - Lyopora regularis Kim., Palaeofavosites cf. alveolaris Gold.; crinoids - Pentagonopentagonalis aff. sulflabellatus Yelt. and others.

Age

Late Ordovician age is established by corals

Age Span:

Beginning stage:

Katian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

448.98

Ending stage:

Hirnantian

Fraction up in the ending stage:

1.0

Ending date (Ma):

443.07

Depositional setting

Depositional pattern:

Additional Information

Compiler:

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