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3.1.2. Huy Formation - HUY

Authors: Malaise, 1888, 1910; Martin, 1969a; Servais & Maletz, 1992.

Description: Black, silky, finely micaceous shale, with cone-in-cone structures and white-veined blackish quartzite beds (Malaise, 1900); fine-grained and slightly micaceous black slate or shale (Martin, 1969a); dark or greyish black graptolitic mudstone (Servais & Maletz, 1992).

Stratotype: Huy, Meuse valley, in the railway sections east and west of the tunnel between the stations of Huy(-Nord) and Huy-Statte.

Area: Condroz inlier; at Sart-Bernard and at Huy-Statte; in the Wépion borehole the black shale with Didymograptus bifidus rests conformably on the Wépion Fm (Graulich, 1961).

Thickness: >150 m (Michot, 1957); >120 m Wépion borehole (Graulich, 1961).

Age: Graptolites were first attributed completely to the Didymograptus bifidus biozone (lower Llanvirn) (Maillieux, 1926a), but later some lower levels were placed lower down in the top of Didymograptus hirundo biozone (Fennian, late Arenig) (Bulman, 1950); restudy and recollection of the graptolites proved beyond doubt the presence of pendent didymograptids, ranging only in the Abereiddian part of the Llanvirn, other species indicate the D. artus Biozone, lower Abereiddian, lower Arenig (Servais & Maletz, 1992); the characteristic acritarch assemblage indicates a Late Arenig to Early Llanvirn age according to Martin (1965, 1969a) while the rich assemblages studied by Servais and Maletz (1992) restrict the range to the Llanvirn only.

Remarks: Synonyms: Schistes de Huy et de Sart-Bernard (Malaise, 1900); Assise de Huy; possibly synonym of the Sart-Bernard Fm (Michot, 1954; Martin, 1969a), but this is not accepted in Servais and Maletz (1992).

(J. VERNIERS)