Iza Formation

Iza Fm

Period:

Devonian

Age Interval:

Emsian-Eifelian, K8

Province:
Kyzylkum Region

Type Locality and Naming

Along Iza, the mountains of Aristantau, Central Kyzylkum. N.M. Larin, 1989 (495, p. 41-42). Stratotype in the southwestern part of the Aristantau Mountains. Upper formation in East Aristanau Reef Fm(local)

Synonym: Izaskaya Formation, Изаская св.

Lithology and Thickness

Layered, dark gray limestones, red-brown siltstone (aleurolites), interbedded with dolomite packets, brecciated rocks, with lenses and nodules of flint, layered limestones and calcareous siltstone (aleurolites) with rare flint nodules. Thickness 267-762m.

Lithology Pattern:

Sandy limestone

Relationships and Distribution

Lower contact

Normally overlies the Madaniyat Fm

Upper contact

It is normally overlain by the Ayakuduk Fm (165, 495).

Regional extent

Central Kyzylkum, southwestern part of the Aristantau Mountains. In the Muruntau Mountains, the age and facies analog of the Iza Fm is the South Bozdon Fm.

GeoJSON

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Fossils

Contains stromatoporoids - Actinostroma">Actinostroma cladratum Nich., Stachyodes verticillata Mc'Coy; tabulates - Favosites ex gr. goldfussi Orb., Thamnopora ex gr. poliforata Schloth.; brachiopods Conchidiella calvata M. Breiv., C. baschkirica Vern., Gypidula biplicata Schnur. and others; Tentaculites - Nowakia barrandei Bouček et Prantl, N. ex gr. elegans Barr., conodonts - Polygnathus inversus Klapp et John., P. linguiformis bultincki Wedd. and others; Goniatites - Agoniatites (Fidelites) accutus (Barr.), A. (Fidelites) fidelis (Barr.) and others

Age

Fossil data characterizes the age interval of late Emsian, Eifelian, and early Givetian.

Age Span:

Beginning stage:

Emsian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

402.41

Ending stage:

Eifelian

Fraction up in the ending stage:

0.75

Ending date (Ma):

387.55

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)”