Cenozoic

Cretaceous

Jurassic

Triassic

Permian

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

Neoproterozoic

Main source = Baratov, R.B., et al. (1976). Subdivisions of stratified and intrusive rocks of Tajikistan. Publishing House "Donish", Dushanbe, 269 pp. plus tables. Provided by Dr. Jovid Aminov, Nazarbayev University, Astana, Kazakhstan Translated to English by the GeoGPT group, Zhejiang Lab, Hangzhou, China--see About

Select Region(s) to search
Hold Ctrl (Windows/Linux) or Command (Mac) to select multiple

Isfara Formation

Isfara Fm

Period:

Paleogene

Age Interval:

upper Eocene, S2, S3

Province:
North Tajik

Type Locality and Naming

Includes in Fergana Valley, Isfara River

Synonym: Isfara layers (Исфаринские слон)

Reference section:

Lithology and Thickness

Clays, marl, limestones. Due to the common composition of the rocks and the similarity of the faunal complexes, the Isfara Fm and Khanabad Fm are usually mapped together. They are represented by greenish-gray clays, locally containing interlayers of marl, limestones, bentonite clays, claystones, and sandstones. Fergana Basin and Alai Valley Basin, each is 5 to 60 m thick. In the Zaalaik region, claystones and sandstones with interlayers of marl, limestone, and conglomerates prevail. The thickness of the Isfara and Khanaabad layers in the South Gissar and Dushanbe regions is 10-65 m, in the Kafirnigan - 15-115, in the Vakhsh - 20-180, in the Zaalaik 7-15 m.

Lithology Pattern:

Claystone

Relationships and Distribution

Lower contact

The Isfara Fm lies conformably on the underlying Rishtan Fm

Upper contact

Overlain by the Khanabad Fm

Regional extent

Fergana Basin and Alai Valley Basin

GeoJSON

{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[68.81,39.88],[69.03,39.9],[69.45,39.98],[71.41,41.03],[71.78,41.31],[73.02,40.87],[71.84,39.88],[70.94,39.83],[70.1,39.66],[68.92,39.51],[68.44,39.58],[68.41,39.72],[68.54,39.89],[68.81,39.88]]]]}}

Fossils

Bivalves. The Isfara Fm and Khanabad Fm contain numerous and diverse remains of fossil organisms (Buzurukov, 1963; Davidzon, 1970). The most characteristic are representatives of the "Gavelinella wachschica" zone, and from the bivalve and gastropod mollusks Nucula aralensis Luk., Nuculana crispata Koen., Tellina praepostera Koen., Nemocardium cingulatum Goldf., Isocardia eichwaldiana Rom., Corbula conglobata Koen., Ostrea plicata Sol., O. tianschanensis Rom., Pecten subitus Korob., Calyptraea turgaica Ovetsch., Vermetus bognariensis Mant.

Age

Organic remains indicate that the Isfara and Khanaabad layers belong to the upper Eocene and allow them to be correlated with the Almynian stage.

Age Span:

Beginning stage:

Priabonian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

37.71

Ending stage:

Priabonian

Fraction up in the ending stage:

0.5

Ending date (Ma):

35.81

Depositional setting

Depositional pattern:

Additional Information

Compiler:

Bosboom, R., Mandic, O., Dupont‐Nivet, G., Proust, J. N., Ormukov, C., & Aminov, J. (2017). Late Eocene palaeogeography of the proto‐Paratethys Sea in Central Asia (NW China, southern Kyrgyzstan and SW Tajikistan). Geological Society, London, Special Publications, 427, 565–588. https://doi.org/10.1144/SP427.11.

Extracted from Baratov, R. B. (1976). Subdivisions of stratified and intrusive rocks of Tajikistan. Donish, Dushanbe, 276.