Arnasay Formation

Arnasay Fm

Period:

Neogene, Quaternary

Age Interval:

Upper Pliocene-Early Pleistocene, CK1

Province:
Chatkal-Kuramin Region

Type Locality and Naming

Along the Arnasay channel, connecting the Chardara reservoir on the Syrdarya River with Lake Aidar. B.I. Pinhasov, 1985 (145, p.57). Stratotype - well 16, interval 155-342m on the left bank of Arnasay, 15km to the north-east of Lake Tuzkan. Previously included in the Upper Pliocene suite. In N.V. Pitinova (166).

Synonym: Arnasayskaya Suite, Арнасайская св.

Lithology and Thickness

A thick layer of buried alluvium. The section consists of channel grey, micaceous sands, interbedded with floodplain-lake clays and siltstone (aleurolites). Thickness up to 800 m. In the south of the Hungry Steppe, it is facially replaced by brownish-grey molasses of the Upper Tien Shan series of Upper Pliocene-Early Pleistocene age.

Lithology Pattern:

Aus Conglomerate

Relationships and Distribution

Lower contact

Not mentioned.

Upper contact

overlain by Quaternary alluvium

Regional extent

Central part of the Golodnaya Steppe. On the left bank of the Syrdarya, in the north-western part of the Hungry Steppe, its age equivalents are the Pskent, Toityubin, and Tuya-Buguz suites, in the Central Kyzylkum it corresponds to the Dengizkul and Ergashkuduk suites.

GeoJSON

null

Fossils

Contains Upper Pliocene-Early Pleistocene ostracods - Candona elongata (Schn), C. abichi Liv., Darwinula stevensoni (Br. et Robert), Herpetocypris varia Stepan., Cypris mandelstami Lubimova, Zonocypris membranae Liv.

Age

Fossil data indicates Upper Pliocene-Early Pleistocene

Age Span:

Beginning stage:

Piacenzian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

3.60

Ending stage:

Gelasian

Fraction up in the ending stage:

1.0

Ending date (Ma):

1.80

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)”