Muynak Formation

Muynak Fm

Period:

Cretaceous

Age Interval:

Turonian-Coniacian

Province:
E. Uzbekistan - Ustyurt Plateau-Sultanuiznag

Type Locality and Naming

Stratotype - eastern slope of the Muynak Peninsula, 4 km north of the village of Muynak. Used in the legend of the South Pre-Aral Subseries for geological maps of the 1:200000 scale, 1998.

Synonym: Muynak Suite, MYNHAKCKAR CBNTA

Lithology and Thickness

Coastal-marine terrigenous formations. In the stratotype, at the base of the formation, there are greenish-gray, quartz-glauconitic, weakly compacted sandstones (0.6 m) lying with erosion on the underlying clays. At the contact, the sandstone contains unrounded fragments of siliceous rocks. Above - greenish-gray, clayey sandstones. [See also “added info” at bottom of entry.] Thickness 10-35m.

Lithology Pattern:

Sandstone

Relationships and Distribution

Lower contact

Lies with erosion on the Shakhaman Fm

Upper contact

Conformably overlain by the lower carbonate subformation of the “Borehole Carbonate Formation” and the Karateren Fm.

Regional extent

Eastern Ustyurt, South Pre-Aral. Boundary of Middle Tian Shan and Southern Tian Shan ranges.

GeoJSON

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Fossils

The lower layer contains large Oyster valves - Amphidonte asiatica (Arkh.); belemnites - Goniocamax westfalicus mujnakensis Naid.; large Shark tooth - Hispidaspis ex gr. gigas (Ag.), Eostriatolamia sp.; Dinosaur bone fragment - Sauropoda; worm tubes - Serpulidae and bryozoan colonies. The overlying clayey sandstones have Lopha flabeliformis (Mart.), L. vialovi Burk., Exogyra decussata Goldf, Goniocamax ex gr. lundgreni (Stol.).

Age

Belongs to the upper Turonian - Coniacian; According to A.D. Arkhangelsky (65), - to the Aral Senonian.

Age Span:

Beginning stage:

Turonian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

91.65

Ending stage:

Coniacian

Fraction up in the ending stage:

1.0

Ending date (Ma):

85.70

Depositional setting

Coastal marine

Depositional pattern:

Additional Information

In the sections of the Muynak Fm wells, there are greenish-gray sands, sandstones, clays. Contains foraminifers - Spiroplectammina embaensis Mjatl., Sp. praelonga (Reuss), Gaudryina variabiliformis N. Byk., Gavelinella moniliformis (Reuss), G praeinfrasantonica (Mjatl.), Cibicidoides praeeriksdalensis (Vass.), Hedbergella agalarovae (Vass.) and others.

Compiler:

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