Bakhmaltepin Formation

Bakhmaltepin Fm

Period:

Neogene

Age Interval:

Lower Pliocene?, F4

Province:
Fergana

Type Locality and Naming

In the city of Bakhmaltepa, at the eastern end of the Akbel Mountains, Northwest Fergana.

Y.R. Smolnikov et al., 1973, briefly covered by G.Yu. Alferov et al. (61, p.40). Stratotype - Along the Akbel section.

Synonym: Bakhmaltepin (Gypsum-Bearing) Formation, Бахмалтепинская (гипсоносная) св.

Lithology and Thickness

Interbedding of lake clays and red-brown, brownish, and greenish-gray gypsums. Subordinate siltstone (aleurolites) and sandstones. Up to 2500 m.

Lithology Pattern:

Gypsiferous claystone

Relationships and Distribution

Lower contact

Lies with a gradual transition on the Aksuykon Fm (saline).

Upper contact

The boundary between them is extremely conditional, with erosion overlain by the Akchop Fm.

Regional extent

Northwest Fergana, Akbel Mountains, Akchop, Supetau.

GeoJSON

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Fossils

Contains ostracods - Cypris mandelstamina Liib., Limnocyhtere misera Mand., Eucypris numulis Schn., Cyprudeis littoralis (Br.), Ilyocypris Gibba (Rom.). In the intermountain depressions of Tian Shan, the upper part of the section of the series is associated with the richest bone remains of the late hipparion fauna. For example, in the Ortok locality of the Kochkor depression, there are remains of mammals - Gipparion dermatorchinum Setve., G. robustum Nord., Ictitherium cf. wongi Zd., Hyjena sp., Chilotherium cf. halereri Ringstrom., Microstonyx major (Gervais), Paleotragus asiaticus Godina, Gazella dorcadoides Schlos.

Age

It was first identified by N.P. Vasilkovsky (126) as the gypsum-bearing sv. A-2 - Oligocene-lower Miocene. M.N. Gramm (180) considered the gypsum-bearing formation to be an age analogue of the upper part of the Obchak sv. V.I. Popov et al. (166) attributed the gypsum-bearing deposits to the Ezgansk and Surkhob sv. of the miocene. A.A. by ostracods attributed the B. sv. to the upper pliocene. Subsequently, A.A. Bukharina (61) identified the ostracod sv. in the complex (layers) with Cypris mandelstamina and conditionally attributed the sv. to the pre-Akchagyl Miocene-Pliocene age. B.I. Pinhasov (145) conditionally refers the sv. to the lower pliocene, it forms the upper part of the section of the lake gray salt-gypsum formation of the upper miocene-lower pliocene Middle Tian Shan series (145). L.K. Gabunia (455), E.L. Dmitrieva, S.A. Nesmeyanov (193) attribute the Ortok fauna to the Pontian, and the upper boundary of the hipparion fauna of Tian Shan is drawn within the Cimmerian. These data and the overlap of gypsum-bearing deposits by the upper pliocene Akchop sv. allow us to conditionally attribute the B. sv. to the lower Pliocene. Included in the Chatkal-Kuramin series of sheets, m-1:50000, 1998.

Age Span:

Beginning stage:

Zanclean

Fraction up in beginning stage:

0.1

Beginning date (Ma):

5.16

Ending stage:

Zanclean

Fraction up in the ending stage:

1.0

Ending date (Ma):

3.60

Depositional setting

Depositional pattern:

Additional Information

Compiler:

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