5.25 Visé Formation - VIS

Authors: d’Omalius d’Halloy, 1828; Pirlet, 1967b; Poty, 1982, 1991; Barchy & Marion, 2000.

Description: Pale to grey limestones including 4 main facies:

- sedimentary limestone breccias with centimetric to pluridecametric boulders of Frasnian age (“cyclopean breccia”);

- thick-bedded packstones to rudstones, with sedimentary breccias, forming fining-upwards pluridecimetric to metric sequences often laminated in their upper part;

- thick-bedded to massive packstones to rudstones;

- massive algal and bioclastic boundstones forming buildups, rich in fossils (mainly brachiopods).

During the 19th century, the Visé Fm yielded an abundant and diversified macrofauna which was of fundamental importance for the understanding of the palaeontology of the Lower Carboniferous.

Stratotype: “F” to “L” abandoned quarries south of Visé (see Pirlet, 1967b, for their location ), east side of the Meuse valley.

Area: VSA. The formation outcrops only in the Visé area.

Thickness: More than 100 m in the Visé quarries. Because of the strong synsedimentary tectonics of the area (Poty, 1991), the thickness of the formation varies from zero to some hundreds of metres.

Age: Early Moliniacian (late Tournaisian), mid and late Moliniacian (early Visean) and Warnantian (late Visean). Cf4a1 to Cf6dForaminifer Subzones (Kimpe et al., 1978; Paproth et al., 1983), RC4ato RC7b-RC8? Coral Subzones. There are numerous stratigraphic gaps, varying in duration from place to place (Poty, 1991), but the Livian is always absent. The HST of the third-order sequences 4, 5 and 6 have been recognized (Hance et al., 2001).