Alai Fm

Includes in Fergana Valley, Isfara River

Synonym: Alai beds

In Alai-Fergana basin, it is greenish-grey mudstones with grey and white siltstones, marls and limestones, some gypsiferous red mudstone intervals in middle, rich in oysters and other bivalves. 10 – 210 m.

Elsewhere: Lower layer - clays, marls, and limestones, middle layer- limestones, dolomites, gypsum in Qafirnigan region, upper layer - limestones, marls, clays. Alai beds on most of the territory under consideration have a three-layered structure. The lower layer is almost universally composed of clays, marls, and limestones. The structure of the middle layer is highly complex. In the Qafirnigan region, limestones, dolomites, gypsum, clays, and sandstones are widely distributed, while in the Vakhsh and Zaalaik regions, red-colored sandstones and clays are present, occasionally with conglomerates and gypsum. In the Dushanbe and South Nissar regions, sandy carbonate rocks are often enriched with phosphate material, up to the formation of phosphate horizons. The upper part of the Alai beds is composed of limestones, marls, clays, and oyster beds. The thickness of these layers is 50-230 m. In the eastern part of Southwest Tajikistan, there are interlayers of tuffs (Zelenova, 1956).

One of the distinctive features of the Alai beds is the mass development of oyster fauna, represented by remnants of Ostrea turkestanensis Rom., O. turkestanensis baissunensis Bohm., O. afganica Vial., O. multicostata Desh., etc. In addition to oysters, there are (Kahanova, 1959) Lucina consobrina Desh., Tellina donacialis Lam., Cardium porulosum Sol., Cardita viquesneli Arch., Pitar nitidula Desh., P. gumberensis Arch., Pteria elitracea Lam., Pinna margaritacea Lam., Panope intermedia Sow., Turritella soluni Liv., Sucostraca bulbiforme Lam. They correspond to the Simferopol horizon or the Lutetian horizon of the Western European scheme.