Tashkent Loess Formation

Tashkent Loess Fm

Period:

Quaternary

Age Interval:

Neopleistocene Middle member (?), CK12

Province:
Chatkal-Kuramin Region

Type Locality and Naming

Named after the city of Tashkent. T.M. Kremlyakova, B.I. Pinhasov in 2000 (A.I. Kimidr., 2000). Used in the stratigraphic scheme of Quaternary deposits (A.I. Kim et al., 2000).

Synonym: Tashkent Loess Formation, Ташкентская лессовая т.

Lithology and Thickness

Composes low foothill gently undulating plains, the surface of which corresponds geodetically to the IV and V floodplain terraces of the rivers. Cyclic alternation of loess, pale, homogeneous, dusty with rare lenses of sand, with five to seven serozem paleosols, cloddy, with carbonate "cockroaches," weakly expressed illuvial layers, sandy-gravelly sediments at the base. Thickness from units in the Prishashkent Chuly and foothills to 100 m and more near the Syrdarya River valley.

Lithology Pattern:

Aus Conglomerate

Relationships and Distribution

Lower contact

Lies on alluvial gravels of the lower part of the Tashkent, Karnab complexes; in the interfluves of the Prishashkent District on loess of the Kumyshkan Fm, as a component part of the undifferentiated loess formations of the lower-middle member of the Neopleistocene.

Upper contact

The schematic stratigraphic column indicates this is the youngest unit

Regional extent

Basin of the Syrdarya and Zeravshan rivers.

GeoJSON

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Fossils

Age

The age of the T. formation is currently accepted as the middle member of the Neopleistocene: it is known to all as the Tashkent loess formation, the main component part of the Tashkent complex. However, a younger age is not excluded, as recent data suggest that the previously considered coeval Tashkent loess complex is divided into different-aged horizons by paleomagnetic and TL methods. Their age increases with depth from modern (at a depth of up to 5-6 m) to middle Neopleistocene (up to 20-40 m). The lower horizons of loess give an age of about 150,000 years, and the upper, lying under the modern soil, 33,000 years (212).

Age Span:

Beginning stage:

Chibanian

Fraction up in beginning stage:

0.8

Beginning date (Ma):

0.26

Ending stage:

Lt. Pleist.

Fraction up in the ending stage:

0.2

Ending date (Ma):

0.11

Depositional setting

Depositional pattern:

Additional Information

Compiler:

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