Koksay Formation

Koksay Fm

Period:

Ordovician

Age Interval:

Wulian-Middle Ordovician, K3

Province:
Kyzylkum Region

Type Locality and Naming

By the Koksay quarry, Southern Bukantau. S.A. Kushnaryov in 1938, 1940 (260, pp. 173-205).

Synonym: Koksay Suite

Lithology and Thickness

Divided into two sub-suites.

Lower (thickness about 300-500 m) - essentially aleurolitic-slate, represented by micaceous-carbonaceous, carbonaceous-quartz-micaceous, sericite-albite-quartz slates of dark gray, greenish-gray color and slaty oligomictic siltstone (aleurolites) with rare layers of fine-grained sandstones.

Upper (thickness about 200-300m) - more coarse-clastic in composition - various-grained sandstones, interbedded with siltstone (aleurolites) and slates, less frequently layers of various-pebble gravels of gray, dark gray color.

Thickness of entire formation is conditionally 500-800 m.

Lithology Pattern:

Sandy_claystone

Relationships and Distribution

Lower contact

Koksay Fm has tectonic contacts with overlying and underlying formations.

Upper contact

Koksay Fm has tectonic contacts with overlying and underlying formations.

Regional extent

Southern Bukantau, Koksay quarry area, Ulken, Jamankaskyrtau, Turbay, Jetymtau II, southwestern part of the Kokpatas mountain, Boztau.

GeoJSON

null

Fossils

Age

Early-Middle Ordovician age is established by comparison with similar terrigenous formations of the Rohatian Fm of Southern Tamdytau. There are no reliable paleontological determinations that would allow unequivocally speaking about the age. The available information about finds of fossils of different ages requires further study and revision (21; 122; 353; Kuzichkina et al., 1977 F., 1984ф.). Most researchers accepted the age of the suite depending on personal interpretation of contacts, position in the section, and comparison. Yu.A. Likhachev et al. (266) and in the Strat. sl. (441) on the basis of comparison with the Besapan Fm conditionally dated it as early Silurian, A.K. Bukharin et al. (122) - conditionally Middle Ordovician-early Silurian; Ya.B. Aysanov et al. (1986ф.) conditionally late Proterozoic-early Paleozoic, on the State Geol. Map-500 of Uzbekistan (460) the suite is conditionally attributed to Vendian-lower Cambrian.POOR DATING -- For graphics, put as Base Wulian (top of "Lower Cambrian" in older sense? And put as top of Middle Ordovician (base Sandbian).

Age Span:

Beginning stage:

Wulian

Fraction up in beginning stage:

0.0

Beginning date (Ma):