Beshmazar Formation

Beshmazar Fm

Period:

Devonian

Age Interval:

Lower Devonian? (Lower Emsian), U5

Province:
Ustyurt-Sultanuzdag

Type Locality and Naming

Along the Beshmazar spring, Sultanuizdag Mountains, South Pre-Aral. G.Yu. Alferov, A.A. Kulesh, D.A. Rubanov in 1958 (457, pp.108-109)

Synonym: Beshmazarskaya Suite, Бешмазарская св.

Lithology and Thickness

Sandstones, carbonate-bearing siltstones, tuffaceous sandstones, andesitic tuffs, tuffaceous gravelites, and tuff conglomerates. Along the strike to the southeast, the rocks change to quartz–feldspar–biotite and two-mica–elidot–biotite–quartz schists, forming a monotonous sequence in the lower reaches of the Kahralysay. Maximum thickness up to 600 m.

Lithology Pattern:

Fine-grained sandstone

Relationships and Distribution

Lower contact

Tectonic lower contact

Upper contact

Tectonic upper contact

Regional extent

Sultanuizdag Mountains, , from the northern edge of the Tebinbulak intrusion in the northwest to the base of the Jamansay and further southeast to the lower reaches of the Kahralysay.

GeoJSON

null

Fossils

No paleontological remains are found.

Age

The relationships with surrounding formations and the age are debated. K.A. Keshishyan et al. (1995) tentatively assigned a Middle Devonian age based on the conformable bedding on the Jamansai suite (Dzhamansay Fm). Yu.A. Likhachev et al. (266) identified the Beshmazar Fm under the name Kahrallysai suite of the Lower Devonian. Based on refined data on the age of the Dzhamansay Fm (Jamansai Fm) and Sheikh-Dzhaylinsky Fm, there are grounds to tentatively consider the B. suite as Early Devonian in the range of Early Emsian (165). M.A. Akhmedjanov et al. (73) identified the slates of the Beshmazar Fm, developed south of the southern serpentinite belt, as an independent Chashmin Fm of tentatively Archean-Early Proterozoic age, based on the high degree of metamorphism of the rocks. Radiological K-Ar dating ranges from 194-252 million years, which may correspond to the Permian-Triassic period. On the State Geol-Map-500 of Uzbekistan (460), it is assigned to the Lower Devonian with tectonic lower and upper contacts.

Age Span:

Beginning stage:

Emsian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

410.51

Ending stage:

Emsian

Fraction up in the ending stage:

0.5

Ending date (Ma):

402.41

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)”