Baldzhuan Gr

Includes in Khation Region, Sughd Region, Darvaz district, Dushanbe - west Shirkent-Luchob, Dushanbe - east Shirkent-Luchob

[Used the spelling from Bosboom et al., 2017]. Commonly divided into two sub-units, spelled here as an upper Childara Fm (spelling from Chapman et al., 2019) and a lower Kamolin Fm.

Synonym: (mainly alternate English spellings): Baldzhuan Fm, Baldzhuan Complex, Boljuan Fm, Boljuan suite, Больджуанская свита, alternate English usage – Baldshuan Series, Baldshuan Fm (Chaptman et al., 2019); Baljuvon Fm (e.g., Gagala et al., 2020, Tectonics v.39)

In every district, it is composed of characteristic red-colored sandstone to claystone: brick, brick-red, brown-red, etc.

In the northeastern part of the Vakhsh area and in the Kulob district, the Boljuan suite (болъджуанской свите) has a two-member structure. The lower part (Kamolin Fm sub-suite) (камолинская подсвита), with a thickness of 200-550 m, consists of massive or thick-bedded "pillow-like" sandstones with a subordinate amount of clay and mudstone layers. The upper part (Childarin sub-suite = Childara Fm) (чильдаринская подсвита), with a thickness from 230 at the Chuldara village to 950 m in the lower course of the Obimazar river, is made up of alternating every 10 to 70 m sandstones and mudstones with the latter prevailing.

In the Karategin district, the Boljuan Fm (больджуанская свита) is represented by sandstones up to 250-300 m thick, containing layers of clays (Chedia, 1971).

In the Dushanbe district, this formation is also composed of sandstones with frequent layers of clay, often argillaceous. In places, at the base of the suite, lenses of clay breccia and inclusions of malachite are encountered. The thickness of the suite increases from east to west, from 130 m at the city of Ordzhonikidzeabad to 700 m in the valley of the Sherkend River.

In the Kafirnigan and Vakhsh districts (mountain ranges of Aruktau, Payragatau, Aktau, Tabakchi, etc.), the Boljuan Fm (болъджуанская свита) has an indistinct four-membered structure. The first (lower) section is mainly composed of fine- and medium-grained sandstones with rare layers of argillites; the second - argillites. The suite consists of thin-grained sandstones; in the third package, fine and medium-grained sandstones prevail, and in the fourth - again, mudstones. The second package of sandstones is capped by a layer of wind-rounded pebbles, which is a marking feature for the above-mentioned ranges (Melamed, 1963). The thickness of the suite varies from 400 to 1000 m in the Kafirnigan area and from 400 to 1400 m in the Vakhsh. In the western part of the Kafirnigan area, on the northwestern slopes of the Babatag ridge, there is a package of cross-bedded sandstones 650 m thick in the Boljuan Fm (болъджуанской свите).

In the northeast and east of the Kulob district, small gravel conglomerates and gravelites play a significant role in the structure of the Boljuan Fm. The thickness of the suite in the Kulob area is 500 - 1200 m.

In the Darvaz district, the lower part of the Boljuan Fm (больджуанскюй свиты) is formed by sandstones and mudstones with a layer of small gravel conglomerates at the base, and the upper part - by conglomerates with interbeds of sandstones and mudstones. The thickness of the suite increases: from 500 m in the northeast to 2000 m in the south. Near the village of Yol, it again decreases to 300-400 m.

In the Baldzhuan Gr, in various districts of southwestern Tajikistan, pollen has been found belonging to the palynocomplexes «B1» and «B2» (Penikova, Penikov, 1973) with the characteristic taxa for these complexes respectively - Sunguisorba minor Scop. and Ehpedra claricristata Schakhm.