5.28 Sovet Formation - SOV

Authors: de Dorlodot, 1910; Conil, 1967; Segura, 1973; Hance, 1988.

Description: The Sovet Fm overlies the purplish-blue limestones of the Leffe Fm. The lower two-thirds of the unit consists of thin- to medium-bedded, dark-coloured, fine to medium grained, bioclastic limestones (packstones). Ooids and clasts are locally abundant in the lower part. Secondary dolomitization can be important, hampering detailed observation. The upper third of the formation, which corresponds to the Braibant Mbr – BRB (Hance et al. 2001) comprises thick-bedded, crinoidal dolomites with brachiopods and rugose corals capped by a few metres of thick-bedded, light-coloured limestones (packstones to grainstones (with ooids, intraclasts and lithoclasts).

Stratotype: Railway section at Sovet, 5.5 km NW of Ciney.

Area: DSA. The formation characterizes a narrow band, oriented WNW-ESE, forming the transition between inner shelf and outer shelf facies. Towards the border with the inner shelf it is overlain by the Terwagne Fm, whereas towards the outer shelf it is overlain by the Salet Fm. To the south, the Sovet Fm passes laterally into the upper part of the Leffe Fm and into the Molignée Fm

Thickness: In the type section, the formation is 126 m thick.

Age: Moliniacian (latest Tournaisian – early Viséan). The Viséan guide, the foraminifer Eoparastaffella enters in the lower part of the formation. Archaediscids are absent. The corals belong to the lower and upper parts of the RC4bSubzone. The base of the formation corresponds to the HST of the third-order sequence 4 of Hance et al. (2001) and the rest to the sequence 5.