2.5.12 Vissoul Formation - VSS

Authors: Verniers, 1976 ms, 1983a; Verniers & Van Grootel, 1991.

Description: Grey mudslate, mudstone, siltstone and fine sandstone with non-calcareous quartzic pelite in the e-divisions. Sedimentology: alternating distal to slightly proximal turbidites with thin bedded laminated hemipelagites; the Tde sequences are medium thick and the T(b)cde sequences are frequent (about 15 % of all sequences) and normally thicker (± 50 %) than the average Tde sequences; c-divisions are thin (2-8 cm). Lower boundary probably with Les Vallées Fm and upper boundary probably with the Fumal Fm.

Stratotype: quarry behind a house, previously called Cabaret au Congo, hamlet of Vissoul, village of Oteppe, Burdinale valley.

Area: Mehaigne and Burdinale valleys.

Thickness: Recorded sections: 9.4 m; thickness of the outcropping sections: 29.4 m; estimated thickness: >30 m.

Age: Graptolites from the Burdinale valley are not characteristic for one biozone but the assemblage indicates a range from the dubius to the lundgreni biozones, middle Sheinwoodian to lower Homerian (middle to upper Wenlock) (Verniers & Rickards, 1979; Zalasiewicz et al., 1998); the chitinozoans belong to subzone D1 (Verniers, 1982) and to the Cingulochitina cingulata global biozone and possibly the Conochitina pachycephala global biozone of Verniers et al. (1995) spanning the same interval as the graptolites.

Remarks: Synonyms: MB6 fm in Verniers (1981, 1983a); “partie supérieure de l’Assise de Corroy” (Verniers, 1983b).

(J. VERNIERS)