Orkutsay Loess Beds Formation

Orkutsay Loess Beds Fm

Period:

Quaternary

Age Interval:

Holocene, CK11

Province:
Chatkal-Kuramin Region

Type Locality and Naming

At Orkutsay, right tributary of the Chirchik River, southern slope of the Karzhantau Ridge. K. A. Toychiev, 1981(4716, p. 11) in rank. For the first time, the Orkutsay Loess Beds was distinguished by N.P. Vasilykovsky in 1937, as deposits of the Karzhantau terrace and considered by him as an analogue of the Nanai terrace. In 1996, K.A. Toychiev (471v) transferred the Orkutsay Loess Beds to the rank of formation.

Synonym: Orkutsay Loessy Tolsha, Оркутсайская лессовая т.

Lithology and Thickness

Alternation of subaerial cover loess and reddish-brown paleosols with interbeds of light gray illuvial deposits. In the section, XIX buried soil horizons are distinguished, ranging from light gray to reddish-brown. Thickness up to 70m.

Lithology Pattern:

Aus Conglomerate

Relationships and Distribution

Lower contact

Stratigraphically unconformably overlies Neogene and Paleozoic deposits.

Upper contact

Schematic stratigraphic column indicates this is the youngest formation

Regional extent

Pre-Tashkent region, high foothills, upper reaches of the Chirchik River basin.

GeoJSON

null

Fossils

Age

According to the paleontological data by K.A. Toychiev (471a; 471b), the section is magnetized in the direction of the modern magnetic field from top to bottom up to 52 m, below this mark - with normal reversed polarity. The normal zone corresponds to the Brunhes epoch, and the variable - to the Matuyama epoch. The boundary between paleomagnetic epochs passes at a depth of 56 m. At the boundary of 43.5 m, the boundary between the Upper Eopleistocene and Neopleistocene passes, at a depth of 3.5 m - between the Neopleistocene and Holocene (471v). In the upper part of the section, three short-term episodes of reversed polarity are recorded. The last two occurred in the Holocene.

Age Span:

Beginning stage:

Holocene

Fraction up in beginning stage:

0.0

Beginning date (Ma):

0.01

Ending stage:

Holocene

Fraction up in the ending stage:

1.0

Ending date (Ma):

0.00

Depositional setting

Depositional pattern:

Additional Information

Compiler:

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