Kushkumbay Formation

Kushkumbay Fm

Period:

Silurian

Age Interval:

Upper Wenlock, K5

Province:
Kyzylkum Region

Type Locality and Naming

Along the Say of Kushkumbai, S. Tamdytau, C. Kyzylkum. Sh. Sh. Sabdyushov, 1970 (392, p.89). Stratotype in the interfluve of the Says of Kushkumbai and Tyumenbai. In the development of the legend for the geodynamic map of C. Kyzylkum, the Stratigraphic Conference in 1992 decided to remove the term "Kushkumbay Fm" (to avoid confusion in span and age) from use. At the same time, the Wenlock terrigenous deposits were combined under the name Tyumenbaitau Fm, and the Ludlow terrigenous-volcanogenic deposits were distinguished in the Kosbulak Fm.

Synonym: Kushkumbai Suite, Кушкумбайская св.

Lithology and Thickness

Upper part (Thickness 30-40m) - siltstone (aleurolites) and argillites with layers of polymictic sandstones.

Lower part (Thickness 100-120m) - polymictic sandstones, tuff-gravels, small-pebble conglomerates, polymictic and volcanomictic gravels with thin and rare layers of siltstone (aleurolites). Higher up, sandstones and siltstone (aleurolites) with layers of gravels (M. 50-90m) begin to predominate.

Thickness of the suite 180-200m.

Lithology Pattern:

Siltstone

Relationships and Distribution

Lower contact

The lower contact is along discontinuous faults

Upper contact

The upper contact is assumed to be conformable with the Kosbulak Fm.

Regional extent

Northern Tamdytau, basin of the Say of Kushkumbai, from the upper reaches of the Say of Dzhengeldy in the east to the western end of the Tamdytau ridge.

GeoJSON

null

Fossils

The Lower Wenlock age is established by graptolites - Testograptus testis (Barr.), Monograptus flemingi (Salter.), Monoclimacis cf. flumendosae (Lort.) and others, characteristic of the M. testis zone of the Upper Wenlock.

Age

The Lower Wenlock age is established by graptolites. Sh.Sh.Sabdyushov (392) understood the Kushkumbai Fm in the age-span of the Ludlow of the Upper Silurian. Detailed biostratigraphic studies by A.I.Kim et al. (1974) showed that Upper Wenlock, occupying significant areas, Ludlow, and Pridoli formations are included in its composition. In connection with this, A.I.Kim et al., retaining the name Kushkumbai Fm for the Upper Wenlock deposits, distinguished the Ludlow in the Kosbulak Fm, and the Pridoli in the Koskuduk Fm. On the geological map of Ya.B.Aysanov et al. (1986) and the State Geological Map-500 of Uzbekistan (460), the Kushkumbai Fm is accepted in the volume of the Wenlock of the Lower Silurian-Ludlow of the Upper Silurian; A.K.Bukharin et al. (122) and in the Strat. Sl. (443) it was attributed to the Ludlow age. In the monograph (165), it is accepted in the span of the Wenlock.

Age Span:

Beginning stage:

Homerian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

430.62

Ending stage:

Homerian

Fraction up in the ending stage:

1.0

Ending date (Ma):

426.74

Depositional setting

Depositional pattern:

Additional Information

Compiler:

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