Dzhamansay Formation

Dzhamansay Fm

Period:

Devonian

Age Interval:

Lochkovian-Pragian, U5

Province:
Ustyurt-Sultanuzdag

Type Locality and Naming

Along Dzhamansay, Sultanuizdag Mountains. G.Yu. Alferov, A.A. Kulesh, D.A. Rubanov, 1963 (266, pp. 54-57). The stratotype is on the right bank of Jamansay (Dzhamansay). Uppermost formation in Sultanuizdag Gr

Synonym: Dzhamansay Suite, Jamansai Fm, Джамансайская св.

Lithology and Thickness

It is divided into three packages: at the base, package 1 - marbled limestones (Jamansay (Dzhamansay Ridge); package 2 - interbedding of siliceous, quartz-siliceous, quartz-micaceous, carbonaceous-quartz, amphibolite, calcareous slates, and thin layers of marbled limestones; package 3 - siliceous, siliceous-quartz slates with thin layers of marbled limestones and horizons of greenstone-altered effusives (metabasalts). The total thickness is up to 700m.

Lithology Pattern:

Shallow-marine marl

Relationships and Distribution

Lower contact

Along K.A.Keshishyan et al. (1995), it lies conformably on the Sultanuizdag Fm. S.S.Schultz (Jr.) (509) notes the transgressive position on the Sultanuizdag suite. Z.M.Abdurazimova considers the contacts with the underlying and overlying formations to be tectonic.

Upper contact

It is conformably overlain by the Beshmazar Fm. Z.M.Abdurazimova considers the contacts with the underlying and overlying formations to be tectonic.

Regional extent

Sultanuizdag Mountains, from the Tebinbulak Intrusive on the northwest to the left bank of Jamansay and further southeast to the lower reaches of Kahralsay.

GeoJSON

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Fossils

Crinoids Pentagonocyclicus multibifidus crassus Yelt., P. imparus Yelt., P. cf. Discoides Yelt., P. ex gr. costatus Schew., P. ex gr. multiradialis Yelt., P. ex gr medius Yelt., Cyclocyclicus laticanalis Yelt., C. undulatus Yelt., C. vericosus Yelt., Entrochi cf. tornati Quenst., Desmidocrinus sp., Zeravshanocrinus incubus Schew.; tabulates - Squameofavosites sp. ind., Paraheliolites sp. ind., Pachycanalicula? sp. ind.; stromatoporoids - Amphipora sp.; foraminifers - Parastegnammina pseudocamerata Pojark., Vicinisphaera aqualita Antk., Uralinella aff. bicamerata E.Bykova; algae - Parmacaulis sp., Epiphyton sp. from thin layers of marbled limestones.

Age

The Early Devonian (Lochkovian-Pragian) age is substantiated by numerous remains of crinoids. The age of part of the suite, developed in the Dzhamsaya basin, M.A.Akhmedjanov et al. (73) consider as Eifelian. At the same time, M.A.Akhmedjanov et al. (73; 75) based on radiological age determinations by the K-Ar method of amphibole from amphibolite slates (823 million years) distinguished the Kyzylsay suite from the D. suite, conditionally of Archean-Early Proterozoic age in the lower reaches of the homonymous say. Based on these data, O.I.Kim (1974) extended the Proterozoic age to the entire suite, V.V.Mikhailov (460) includes the D. suite in the Sultanuizdag series of the conditional Proterozoic.

Age Span:

Beginning stage:

Lochkovian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

415.70

Ending stage:

Pragian

Fraction up in the ending stage:

1.0

Ending date (Ma):

410.51

Depositional setting

Depositional pattern:

Additional Information

Compiler:

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