Ayakumar Formation

Ayakumar Fm

Period:

Cambrian, Ordovician

Age Interval:

Upper Cambrian-Lower Ordovician [State map has as middle Carboniferous olistostromes (age of displacement; but deposits are U.Camb.], K5a

Province:
Kyzylkum Region

Type Locality and Naming

Along Ayakumar, northern Tamdytau. K. K. Pyatkov et al. in 1969 (1971) within the volume of terrigenous-siliceous-carbonate and "tillite-like" formations of the upper Cambrian.

Synonym: Ayakumar Suite, Аякумарская св.

Lithology and Thickness

Clayey slates and argillites are greenish-gray, dark gray, gray, interbedded with clayey-siliceous slates, clayey-dolomitic limestones, and rare layers of dark quartz-siliceous rock. Thickness no more than 100 m.

Lithology Pattern:

Clayey limestone

Relationships and Distribution

Lower contact

Upper contact

Regional extent

The northwestern and central parts of northern Tamdytau in tectonic blocks, scales, developed along the seams of gentle overthrusts. The middle part of the suite is correlated with the Badamchaly suite of the S. Nuratau ridge.

GeoJSON

null

Fossils

Contains in the lower part of the section Late Cambrian conodonts - Oneotodus cf. gallatini Müller., Proconodontus cf. mülleri Miller, Pr. tricarinatus (Nog.), Pr. tenuis (Müller), Pr. cf. rotundatus (Dr. et Jon.), Eoconodontus cf. notchpeakensis Miller; in the upper part Early Ordovician - Drepanodus subarcuatus Pand., Dr. cf. arcuatus Pand., Oistodus parallelus Pand. and others.

Age

The Ayakumar Fm is considered within the span of Lower Paleozoic terrigenous-carbonate deposits without the clastic part and "tillite-like" formations, which, according to K.K. Pyatkov et al., are attributed to the olistostromal t. of the upper part of the middle Carboniferous. There is still no consensus on the structure of the Ayakumar Fm section and its age. Sh.Sh. Sabdyushev et al. (1970) considered the deposits of the suite, in the understanding of K.K. Pyatkov et al., to be included in the melange zones. I.A. Poniklensky, G.V. Bolgova et al. (1975) proved that the section of the Ayakumar Fm consists of tectonic blocks and scales of stratified deposits of the Cambrian and Ordovician, which within the "melange zone" were mapped and paleontologically characterized by them. K. K. Pyatkov et al. (1975) consider the Ayakumar Fm as an olistostromal thickness of the upper Carboniferous - lower Permian (?); A.K. Bukharin et al. (122) - as a middle Carboniferous olistostrome, composed of limestone-slate formations with frequent pebbles, boulders, blocks of rocks of different ages, immersed in an aleuro-pelitic matrix; Z.M. Abdouazimova et al. (1993) attributed only terrigenous-carbonate deposits of the upper Cambrian-Ordovician to the Ayakumar Fm, characterized by numerous Late Cambrian and Early Ordovician conodonts, the rest of the suite in the previous understanding was attributed to the olistostromal formations of the middle Carboniferous. In the same volume, it is accepted in the monograph (165). On the State Geolmap-500 of Uzbekistan (460), the Ayakumar Fm is distinguished as a middle Carboniferous olistostrome.

Age Span:

Beginning stage:

Jiangshanian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

494.20

Ending stage:

Tremadocian

Fraction up in the ending stage:

1.0

Ending date (Ma):

477.08

Depositional setting

Depositional pattern:

Additional Information

Compiler:

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