Type Locality and Naming
Along the Aktau mountain, S. Nuratau ridge. I.A. Pyanovskaya et al., 1986 (371, pp.53-59).
Synonym: Aktau Series, Актауская сер., Aktau marbles, Aktau Fm, Aktaw Gr, Aktaw marbles
Lithology and Thickness
Includes (in ascending order) Angidan Fm, Charhansay Fm, and Bahiltau Fm.
These formations were first described by V.A. Nikolayev in 1925 (331) as "Aktau marbles." Later, they were described as formations, with their age and stratigraphic position interpreted differently.
Marbles, marblized limestones with lenticular bodies of corundum and emery, microquartzites, sandstones, conglomerates. Thickness up to 2000m. All rocks have undergone contact metamorphism, resulting in the recrystallization of organic remains and their poor preservation.
Age
N.A. Smirnov (382), G.S. Chikryov and Kh.V. Ryskina (497) considered the carbonate rocks to be overlying the sandy-slate deposits of the Lower Silurian and attributed them to the Middle Paleozoic, Upper Silurian-Lower Devonian; according to V.N. Nikolayev (331), Yu.A. Likhachev, and others (266), they were the lower member of the Paleozoic section in Southern Nuratau and were dated to the Lower Paleozoic, Ordovician-Silurian (?); K.K. Pyatkov (375) believed that the Lower Silurian rocks, previously considered as the wings of an anticlinal structure, were thrust over the Early Devonian-Carboniferous Aktau marbles. Subsequent geological and thematic works by S.K. Pivnya et al. (1976), K.K. Pyatkov et al. (1975), I.A. Pyanovskaya (371), Yu.V. Shumakov, L.N. Skakun et al. (1984), V.S. Korsakov et al. (1993), R.R. Usmanov et al. (1999) divided the deposits attributed to the Aktau Gr into three suites, providing additional paleontological characteristics that allowed determining their age and position in the Paleozoic section. R.S. Khan et al. (1989) classified all marbles and marblized limestones as part of the Aktau Gr of the Silurian-Carboniferous, and the meta-terrigenous and meta-terrigenous-carbonate packets among them were attributed to the Darasay Fm of the Middle Carboniferous.
